Revert of Adding Site Isolation Win bot filtering for...

Revert of Adding Site Isolation Win bot filtering for WindowOpenPanelTest.WindowOpenFocus. (patchset #1 id:1 of https://codereview.chromium.org/2269523003/ )

Reason for revert:
The filter file is apparently not needed anymore: despite the fact that the test got renamed in r413759, we are not seeing failures in the WindowOpenFocus test in the latest builds on Site Isolation Win bot.

Original issue's description:
> Adding Site Isolation Win bot filtering for WindowOpenPanelTest.WindowOpenFocus.
>
> BUG=639510
>
> Committed: https://crrev.com/a98073ac85514395939268f9d71a5d609867d450
> Cr-Commit-Position: refs/heads/master@{#413773}

TBR=creis@chromium.org
# Not skipping CQ checks because original CL landed more than 1 days ago.
BUG=639510

Review-Url: https://codereview.chromium.org/2287743002
Cr-Commit-Position: refs/heads/master@{#414857}

testing/buildbot/chromium.fyi.json

@@ -10899,8 +10899,7 @@
       },
       {
         "args": [
-          "--isolate-extensions",
-          "--test-launcher-filter-file=src/testing/buildbot/filters/isolate-extensions.interactive_ui_tests.filter"
+          "--isolate-extensions"
         ],
         "test": "interactive_ui_tests"
       },

testing/buildbot/filters/isolate-extensions.interactive_ui_tests.filter

-# crbug.com/639510: WindowOpenPanelTest.WindowOpenFocus timing out on the
-# Site Isolation Win bot
--WindowOpenPanelTest.WindowOpenFocus