Remove test triggering from mac-arm64-rel.

The tests are run from mac-arm64-rel-tests now and don't need
to be isolated using workarounds on the mac-arm64-rel side.

TBR=gbeaty@chromium.org

Bug: 1117252
Change-Id: Ia54bba134e304f3c4ffe395358a95ce7dbcbbf66
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2407293Reviewed-by: Erik Staab <estaab@chromium.org>
Commit-Queue: Erik Staab <estaab@chromium.org>
Cr-Commit-Position: refs/heads/master@{#806432}

testing/buildbot/waterfalls.pyl

@@ -4637,19 +4637,6 @@
         'additional_compile_targets': [
           'all',
         ],
-        'os_type': 'mac',
-        'browser_config': 'release',
-        # TODO(thakis): This mixin is almost certainly incorrect. It exists to
-        # make the test suites listed below be valid; this can't be generated
-        # swarming dimensions are set.
-        'mixins': [
-          'mac_mini_intel_gpu_stable',
-        ],
-        'test_suites': {
-          'gtest_tests': 'gpu_fyi_mac_release_gtests',
-          'gpu_telemetry_tests': 'gpu_fyi_mac_release_telemetry_tests',
-          'isolated_scripts': 'rendering_desktop_representative_perf_tests_isolated_scripts',
-        },
       },
     },
   },