ci: Fix snapcraft promote rc job

.github/workflows/release.yaml

@@ -160,8 +160,7 @@ jobs:
         run: sudo apt-get update && sudo apt-get install -y expect
       - name: Promote Snap
         run: |
-          RELEASE_TYPE=$(echo "${{ github.ref }}" | awk -F"/" '{print $3}')
+          if [[ $GITHUB_REF_NAME == rc* ]]; then
-          if [ "$RELEASE_TYPE" = "rc" ]; then
               expect -c "
               spawn snapcraft promote fluffychat --from-channel edge --to-channel candidate
               expect \"Do you want to promote the current set to the 'candidate' channel? [y/N]:\"