fix(ci): add explicit ref:main for cross-repo checkout

actions/checkout@v3 fails when querying the default branch for a
different repository. Explicitly specifying ref:main skips the API
discovery that was returning 'Not found'.

.gitea/workflows/build.yaml

@@ -21,6 +21,7 @@ jobs:
           repository: b3nw/schwab-scraper
           path: vendor/schwab-scraper
           token: ${{ secrets.CR_PAT }}
+          ref: main
 
       - name: Login to Gitea Container Registry
         uses: docker/login-action@v2