Fix telemetry_perf_unittests with newer mock version

Fixes a typo in update_wpr_unittest.py that causes a test to fail with
newer versions of the mock library due to assert_not_called actually
working properly in newer versions.

Bug: 1156832
Change-Id: Ic980f181ca18c3b0e2148fcdbd35fde39bd5c1be
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2587756
Commit-Queue: Brian Sheedy <bsheedy@chromium.org>
Commit-Queue: John Chen <johnchen@chromium.org>
Auto-Submit: Brian Sheedy <bsheedy@chromium.org>
Reviewed-by: John Chen <johnchen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#836779}

tools/perf/cli_tools/update_wpr/update_wpr_unittest.py

@@ -280,7 +280,7 @@ class UpdateWprTest(unittest.TestCase):
   def testDoesNotDeleteReusedWpr(self, os_remove):
     self._open.return_value.__enter__.return_value.read.return_value = (
         '{"archives": {"<story>": {"DEFAULT": "<archive>"}, '
-        '"<other>": {"DEFAULT": "foo", "linux": "<arhive>"}}}')
+        '"<other>": {"DEFAULT": "foo", "linux": "<archive>"}}}')
     self.wpr_updater._DeleteExistingWpr()
     os_remove.assert_not_called()