fix: override runner to ubuntu-latest for public repo CI

The CI Standard Checks workflow has been timing out after 24 hours
since March 27. The reusable workflow defaults to ci-base-scale-set
(self-hosted runners), which are restricted to private repos.

This change explicitly specifies ubuntu-latest (GitHub-hosted runners)
for this public repository.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: pannago

.github/workflows/ci-standard-checks.yml

@@ -15,3 +15,5 @@ on:
 jobs:
   ci-standard-checks:
     uses: Typeform/.github/.github/workflows/ci-standard-checks-workflow.yaml@v1
+    with:
+      runner: ubuntu-latest