compositor: Remove the is_running_problem_test setting (#31589)

These tests don't seem to time out any longer and this mechanism is
probably better served by some sort of adjustment to `RUST_LOG` in the
WPT harness.

components/servo/lib.rs

@@ -460,7 +460,6 @@ where
                 webxr_main_thread,
             },
             composite_target,
-            opts.is_running_problem_test,
             opts.exit_after_load,
             opts.debug.convert_mouse_to_touch,
             top_level_browsing_context_id,
@@ -992,7 +991,6 @@ fn create_constellation(
         initial_window_size,
         opts.random_pipeline_closure_probability,
         opts.random_pipeline_closure_seed,
-        opts.is_running_problem_test,
         opts.hard_fail,
         !opts.debug.disable_canvas_antialiasing,
         canvas_create_sender,