[webauthn] Add WPT folder to WebAuthn WATCHLIST

Bug: 1011029
Change-Id: I0828fd90ad18d6233a61c9e58c600485f71eef76
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1838353
Commit-Queue: Nina Satragno <nsatragno@chromium.org>
Commit-Queue: Martin Kreichgauer <martinkr@google.com>
Auto-Submit: Nina Satragno <nsatragno@chromium.org>
Reviewed-by: Martin Kreichgauer <martinkr@google.com>
Cr-Commit-Position: refs/heads/master@{#702509}

WATCHLISTS

@@ -1867,6 +1867,7 @@
                     '|content/browser/webauth/'\
                     '|device/fido/'\
                     '|third_party/blink/public/mojom/webauthn/'\
+                    '|third_party/blink/web_tests/external/wpt/webauthn/'\
                     '|third_party/microsoft_webauthn/',
     },
     'webgpu': {