chore: ignore updates to microsoft/playwright-github-action

Microsoft publishes updates to this action using the same scheme
as GitHub, where the v1 tag is updated to the latest release of
the 1.0 series. Therefore, we can manage updates manually.

Author: jawnsy

.github/dependabot.yml

@@ -10,6 +10,7 @@ updates:
       # release tag, so handle updates manually
       - dependency-name: "actions/*"
       - dependency-name: "github/codeql-action/*"
+      - dependency-name: "microsoft/playwright-github-action"
 
   - package-ecosystem: "npm"
     directory: "/"