Update doc-build.yml (#10596)

Add ability to build docs with manual workflow

Author: metascroy

.github/workflows/doc-build.yml

@@ -89,7 +89,7 @@ jobs:
 
   upload-gh-pages:
     needs: build
-    if: github.repository == 'pytorch/executorch' && github.event_name == 'push' && (github.ref == 'refs/heads/main' || startsWith(github.ref, 'refs/tags/v'))
+    if: github.repository == 'pytorch/executorch' && ((github.event_name == 'push' && (github.ref == 'refs/heads/main' || startsWith(github.ref, 'refs/tags/v'))) || (github.event_name == 'workflow_dispatch' && github.ref == 'refs/heads/release/0.6'))
     permissions:
       id-token: write
       contents: write