[weblayer, skew tests] Refresh skew tests for M87

This CL will add skew tests for version 87.0.4280.121.

TBR=sky@chromium.org

Bug: 1041619
Change-Id: I167b3eb99bebc9c6a30005e9e6746967605eccf8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2596824
Commit-Queue: Rakib Hasan <rmhasan@google.com>
Reviewed-by: Rakib Hasan <rmhasan@google.com>
Cr-Commit-Position: refs/heads/master@{#837921}

testing/buildbot/variants.pyl

@@ -342,13 +342,13 @@
       '../../weblayer/browser/android/javatests/skew/expectations.txt',
       '--impl-version=87',
     ],
-    'identifier': 'M87_Implementation_Library_Tests',
+    'identifier': 'Implementation Tests For 87.0.4280.121',
     'swarming': {
       'cipd_packages': [
         {
           'cipd_package': 'chromium/testing/weblayer-x86',
           'location': 'weblayer_instrumentation_test_M87',
-          'revision': 'version:87.0.4280.108',
+          'revision': 'version:87.0.4280.121',
         }
       ],
     },
@@ -411,13 +411,13 @@
       '../../weblayer/browser/android/javatests/skew/expectations.txt',
       '--client-version=87',
     ],
-    'identifier': 'M87_Client_Library_Tests',
+    'identifier': 'Client Tests For 87.0.4280.121',
     'swarming': {
       'cipd_packages': [
         {
           'cipd_package': 'chromium/testing/weblayer-x86',
           'location': 'weblayer_instrumentation_test_M87',
-          'revision': 'version:87.0.4280.108',
+          'revision': 'version:87.0.4280.121',
         }
       ],
     },