Revert "Actions, alpha build: try passing in a different prerelease_identifier"

This reverts commit de0d8cf.

Author: michaelklishin

.github/workflows/alpha-build.yaml

@@ -21,4 +21,4 @@ jobs:
             -H "Authorization: Bearer ${{ secrets.RABBITMQCI_BOT_TOKEN }}" \
             -H "X-GitHub-Api-Version: 2022-11-28" \
             https://api.github.com/repos/rabbitmq/server-packages/dispatches \
-            -d '{"event_type": "new_4.1.x_alpha", "client_payload": {"prerelease": true, "prerelease_kind": "alpha", "prerelease_identifier": "${{ $SHORT_SHA }}", "base_version": "4.1.0"}}'
+            -d '{"event_type": "new_4.1.x_alpha", "client_payload": {"prerelease": true, "prerelease_kind": "alpha", "prerelease_identifier": "${{ env.SHORT_SHA }}", "base_version": "4.1.0"}}'