Bug 1839378 - don't run perfdocs-verify task for changes in testing/web-platform/ folder. r=andi DONTBUILD

jgraham confirmed there is nothing related in this directory, and any update
to wpt test expectations scheduled the task.

Differential Revision: https://phabricator.services.mozilla.com/D181475

taskcluster/ci/source-test/mozlint.yml

@@ -537,9 +537,7 @@ perfdocs-verify:
             - 'taskcluster/**'
             - '**/perftest.ini'
             - 'python/mozperftest/**'
-            - 'testing/**/*.ini'
-            - 'testing/**/*.yml'
-            - 'testing/**/*.rst'
+            - 'testing/{,!(web-platform)/{,**/}}*.{ini,rst,yml}'
             - 'tools/lint/perfdocs.yml'