Update GitHub Actions workflows. (#456)

This PR was automatically generated by the
update-workflows-ecosystem-providers workflow in the pulumi/ci-mgmt
repo, from commit 6eed05751ff69ae8a0914853dd91bee74dc7f0bb.

.github/workflows/check-upstream-upgrade.yml

@@ -20,7 +20,7 @@ jobs:
       run: git fetch --prune --unshallow --tags
       shell: bash
     - name: Install upgrade-provider
-      run: go install github.com/pulumi/upgrade-provider@29dae5201e3ded4c5bd34d82adbef18ba1e12df8
+      run: go install github.com/pulumi/upgrade-provider@main
       shell: bash
     - name: "Set up git identity: name"
       run: git config --global user.name pulumi-bot