Confirming this 'core_updater.lock'. It may not be obvious at first but look at the line 771.

File: wp-admin/includes/class-wp-upgrader.php
754:    /**
755:     * Creates a lock using WordPress options.
756:     *
757:     * @since 4.5.0
758:     * @access public
759:     * @static
760:     *
761:     * @param string $lock_name       The name of this unique lock.
762:     * @param int    $release_timeout Optional. The duration in seconds to respect an existing lock.
763:     *                                Default: 1 hour.
764:     * @return bool False if a lock couldn't be created or if the lock is no longer valid. True otherwise.
765:     */
766:    public static function create_lock( $lock_name, $release_timeout = null ) {
767:        global $wpdb;
768:        if ( ! $release_timeout ) {
769:            $release_timeout = HOUR_IN_SECONDS;
770:        }
771:        $lock_option = $lock_name . '.lock';
772: 
773:        // Try to lock.
774:        $lock_result = $wpdb->query( $wpdb->prepare( "INSERT IGNORE INTO `$wpdb->options` ( `option_name`, `option_value`, `autoload` ) VALUES (%s, %s, 'no') /* LOCK */", $lock_option, time() ) );
775: 

Now, if you like you may delete this option:

$>wp option delete my_option

Confirming this 'core_updater.lock'. It may not be obvious at first but look at the line 771.

File: wp-admin/includes/class-wp-upgrader.php
754:    /**
755:     * Creates a lock using WordPress options.
756:     *
757:     * @since 4.5.0
758:     * @access public
759:     * @static
760:     *
761:     * @param string $lock_name       The name of this unique lock.
762:     * @param int    $release_timeout Optional. The duration in seconds to respect an existing lock.
763:     *                                Default: 1 hour.
764:     * @return bool False if a lock couldn't be created or if the lock is no longer valid. True otherwise.
765:     */
766:    public static function create_lock( $lock_name, $release_timeout = null ) {
767:        global $wpdb;
768:        if ( ! $release_timeout ) {
769:            $release_timeout = HOUR_IN_SECONDS;
770:        }
771:        $lock_option = $lock_name . '.lock';
772: 
773:        // Try to lock.
774:        $lock_result = $wpdb->query( $wpdb->prepare( "INSERT IGNORE INTO `$wpdb->options` ( `option_name`, `option_value`, `autoload` ) VALUES (%s, %s, 'no') /* LOCK */", $lock_option, time() ) );
775: 

Now, if you like you may delete this option:

$>wp option delete core_updater.lock

Confirming this 'core_updater.lock'. It may not be obvious at first but look at the line 771.

File: wp-admin/includes/class-wp-upgrader.php
754:    /**
755:     * Creates a lock using WordPress options.
756:     *
757:     * @since 4.5.0
758:     * @access public
759:     * @static
760:     *
761:     * @param string $lock_name       The name of this unique lock.
762:     * @param int    $release_timeout Optional. The duration in seconds to respect an existing lock.
763:     *                                Default: 1 hour.
764:     * @return bool False if a lock couldn't be created or if the lock is no longer valid. True otherwise.
765:     */
766:    public static function create_lock( $lock_name, $release_timeout = null ) {
767:        global $wpdb;
768:        if ( ! $release_timeout ) {
769:            $release_timeout = HOUR_IN_SECONDS;
770:        }
771:        $lock_option = $lock_name . '.lock';
772: 
773:        // Try to lock.
774:        $lock_result = $wpdb->query( $wpdb->prepare( "INSERT IGNORE INTO `$wpdb->options` ( `option_name`, `option_value`, `autoload` ) VALUES (%s, %s, 'no') /* LOCK */", $lock_option, time() ) );
775: 

Confirming this 'core_updater.lock'. It may not be obvious at first but look at the line 771.

File: wp-admin/includes/class-wp-upgrader.php
754:    /**
755:     * Creates a lock using WordPress options.
756:     *
757:     * @since 4.5.0
758:     * @access public
759:     * @static
760:     *
761:     * @param string $lock_name       The name of this unique lock.
762:     * @param int    $release_timeout Optional. The duration in seconds to respect an existing lock.
763:     *                                Default: 1 hour.
764:     * @return bool False if a lock couldn't be created or if the lock is no longer valid. True otherwise.
765:     */
766:    public static function create_lock( $lock_name, $release_timeout = null ) {
767:        global $wpdb;
768:        if ( ! $release_timeout ) {
769:            $release_timeout = HOUR_IN_SECONDS;
770:        }
771:        $lock_option = $lock_name . '.lock';
772: 
773:        // Try to lock.
774:        $lock_result = $wpdb->query( $wpdb->prepare( "INSERT IGNORE INTO `$wpdb->options` ( `option_name`, `option_value`, `autoload` ) VALUES (%s, %s, 'no') /* LOCK */", $lock_option, time() ) );
775: 

Now, if you like you may delete this option:

$>wp option delete my_option