Revert "Add tests to Fuchsia ARM64 CI builder."

This reverts commit 4486011f.

Reason for revert: See crbug.com/1054837

Original change's description:
> Add tests to Fuchsia ARM64 CI builder.
> 
> Use the same test exceptions for Fuchsia ARM64 as fuchsia-fyi-arm64-rel.
> 
> Bug: 1042512
> Change-Id: I7b9333e49151975b4bfecb98dd6d36d954b514ef
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2067673
> Reviewed-by: John Budorick <jbudorick@chromium.org>
> Commit-Queue: Stephen Roe <steveroe@google.com>
> Cr-Commit-Position: refs/heads/master@{#743555}

TBR=martiniss@chromium.org,jbudorick@chromium.org,steveroe@google.com

Change-Id: Id61a07e464d238b7007e18625f19a549cd249b05
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 1042512
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2067091Reviewed-by: Mason Freed <masonfreed@chromium.org>
Reviewed-by: John Budorick <jbudorick@chromium.org>
Commit-Queue: Mason Freed <masonfreed@chromium.org>
Cr-Commit-Position: refs/heads/master@{#743582}

testing/buildbot/test_suite_exceptions.pyl

@@ -364,7 +364,6 @@
   'components_unittests': {
     'remove_from': [
       'Fuchsia x64', # https://crbug.com/961457
-      'Fuchsia ARM64', # https://crbug.com/961457
       'android-code-coverage-native', # crbug/1018431
       'fuchsia-fyi-arm64-rel',  # https://crbug.com/961457
       'fuchsia-fyi-x64-dbg',  # https://crbug.com/961457
@@ -1039,7 +1038,6 @@
   'net_unittests': {
     'remove_from': [
       'chromeos-amd64-generic-rel',  # https://crbug.com/1053547
-      'Fuchsia ARM64',  # https://crbug.com/877248
       'fuchsia-fyi-arm64-rel',  # https://crbug.com/877248
       'fuchsia-fyi-x64-dbg',  # https://crbug.com/844416
     ],

testing/buildbot/waterfalls.pyl

@@ -3585,14 +3585,6 @@
         'additional_compile_targets': [
           'all',
         ],
-        'test_suites': {
-          'gtest_tests': 'fuchsia_gtests',
-        },
-        'mixins': [
-          'arm64',
-          'docker',
-          'linux-xenial',
-        ],
       },
       'Fuchsia x64': {
         'additional_compile_targets': [