You are trying to unhook a PHP *function* as opposed to a (class) instance method - see here:

    array( $this, 'job_manager_job_filters_distance' )

...that's the *actual* callback registered to the hook. To unhook you need the same (a reference to the instance).

If you are trying to unhook from *within* the class, it's as easy as using the above. Otherwise you need a reference to the instance - look for something like the following in your code:

    $my_class = new Name_Of_Class;

...then you'd run:

    remove_action( 'job_manager_job_filters_search_jobs_end', array( $my_class, 'job_manager_job_filters_distance' ) , 0 );