Use node20

use node20

In this PR https://github.com/Staffbase/github-action-jira-release-tagging/pull/114/files i changed the used node version for the action to node21. This was wrong ans stated in the frontend workflow now

https://github.com/Staffbase/frontend/actions/runs/8249283571/job/22561334164

action.yml

@@ -20,5 +20,5 @@ inputs:
     description: "Whether to notify user watching the Jira issues, default is 'false'"
     required: false
 runs:
-  using: 'node21'
+  using: 'node20'
   main: './dist/index.js'