Don't update krew manifest for pre-releases

Signed-off-by: Tamal Saha <tamal@appscode.com>

Author: tamalsaha

.github/workflows/release.yml

@@ -70,7 +70,7 @@ jobs:
         env:
           GITHUB_USER: 1gtm
           GITHUB_TOKEN: ${{ secrets.LGTM_GITHUB_TOKEN }}
-        if: startsWith(github.ref, 'refs/tags/')
+        if: startsWith(github.event.ref, 'refs/tags/') && (contains(github.ref, '-alpha.') || contains(github.ref, '-beta.') || contains(github.ref, '-rc.')) == false
         run: |
           cd $RUNNER_WORKSPACE/krew-index
           ./hack/scripts/open-pr.sh $GITHUB_WORKSPACE stash