Do not delete branches from the WPT exporter

GitHub now deletes branches automatically when a PR is merged. As such,
the exporter should no longer try to delete them.

Bug: 1032079
Change-Id: I404764eec3d9abfccd7f128dcd52897b9ac06a2d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1955337Reviewed-by: Luke Z <lpz@chromium.org>
Reviewed-by: Robert Ma <robertma@chromium.org>
Commit-Queue: Robert Ma <robertma@chromium.org>
Cr-Commit-Position: refs/heads/master@{#723474}

third_party/blink/tools/blinkpy/w3c/test_exporter.py

@@ -214,12 +214,6 @@ class TestExporter(object):
 
         try:
             self.wpt_github.merge_pr(pull_request.number)
-
-            # This is in the try block because if a PR can't be merged, we shouldn't
-            # delete its branch.
-            _log.info('Deleting remote branch %s...', branch)
-            self.wpt_github.delete_remote_branch(branch)
-
             change_id = self.wpt_github.extract_metadata('Change-Id: ', pull_request.body)
             if change_id:
                 cl = GerritCL(data={'change_id': change_id}, api=self.gerrit)

third_party/blink/tools/blinkpy/w3c/test_exporter_unittest.py

@@ -181,7 +181,6 @@ class TestExporterTest(LoggingTestCase):
             # removed it from.
             'get_pr_branch',
             'merge_pr',
-            'delete_remote_branch',
             # 5. #458479
             'pr_for_chromium_commit',
             'get_pr_branch',
@@ -348,7 +347,6 @@ class TestExporterTest(LoggingTestCase):
             'pr_for_chromium_commit',
             'get_pr_branch',
             'merge_pr',
-            'delete_remote_branch',
         ])
         self.assertEqual(test_exporter.wpt_github.pull_requests_created, [])
         self.assertEqual(test_exporter.wpt_github.pull_requests_merged, [1234])