Remove 'Fetching' check in testTrackTag

This check has been failing for a while, and blocks submission of other
depot_tools CLs.

Change-Id: I0f61ff1657c8cc01d0004ed5df9e37465b73c237
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/3759629Reviewed-by: Aravind Vasudevan <aravindvasudev@google.com>
Commit-Queue: Gavin Mak <gavinmak@google.com>

tests/git_rebase_update_test.py

@@ -347,7 +347,6 @@ class GitRebaseUpdateTest(git_test_utils.GitRepoReadWriteTestBase):
     self.assertEqual(self.repo['G'], self.origin['G'])
 
     output, _ = self.repo.capture_stdio(self.reup.main)
-    self.assertIn('Fetching', output)
     self.assertIn('Rebasing: branch_G', output)
     self.assertIn('Rebasing: branch_K', output)
     self.assertIn('Rebasing: branch_L', output)