Fix concurrency issue with pr-merge workflow by hardcoding validate's workflow name. This is because github.workflow is inherited from calling workflows and can result in errors like:
Canceling since a deadlock for concurrency group 'Post PR Merge-refs/heads/main' was detected between 'top level workflow' and 'validate'
Description
Fix concurrency issue with pr-merge workflow by hardcoding validate's workflow name. This is because github.workflow is inherited from calling workflows and can result in errors like: