Revert nightly job to use release 1.91 (#20027)

Author: mustard-mh

.github/workflows/code-nightly.yml

@@ -35,7 +35,7 @@ jobs:
         run: |
           export LEEWAY_WORKSPACE_ROOT=$GITHUB_WORKSPACE
 
-          codeHeadCommit=$(curl -H 'Accept: application/vnd.github.VERSION.sha' https://api.github.com/repos/gitpod-io/openvscode-server/commits/gp-code/main)
+          codeHeadCommit=$(curl -H 'Accept: application/vnd.github.VERSION.sha' https://api.github.com/repos/gitpod-io/openvscode-server/commits/gp-code/release/1.91)
           codeVersion=$(curl https://raw.githubusercontent.com/gitpod-io/openvscode-server/$codeHeadCommit/package.json | jq .version)
           imageRepoBase=${{ github.ref == 'refs/heads/main' && 'eu.gcr.io/gitpod-core-dev/build' || 'eu.gcr.io/gitpod-dev-artifact/build' }}
           cd components/ide/code