github workflow: Update buildcheck.yaml

Yaml was assuming "master" as name of working branch. In this project we have the newer "main". So correct the yaml

Signed-off-by: Stephen Lawrence <[email protected]>

.github/workflows/buildcheck.yaml

@@ -25,7 +25,7 @@ jobs:
 
       - name: Deploy docs
         # Only deploy docs if this was a push to master
-        if: ${{ github.event_name == 'push' && github.ref == 'refs/heads/master' }}
+        if: ${{ github.event_name == 'push' && github.ref == 'refs/heads/mainr' }}
         uses: JamesIves/[email protected]
         with:
           branch: gh-pages # The branch the action should deploy to.