Clean BRANCH variable definition

Author: sarahchen6

.github/workflows/create-release-branch.yaml

@@ -42,8 +42,7 @@ jobs:
         id: define-branch
         run: |
           TAG=${{ steps.determine-tag.outputs.tag }}
-          BRANCH="release/${TAG%.0}.x"
-          echo "branch=${BRANCH}" >> "$GITHUB_OUTPUT"
+          echo "branch=release/${TAG%.0}.x" >> "$GITHUB_OUTPUT"
 
       - name: Checkout dd-trace-java at tag
         uses: actions/checkout@08c6903cd8c0fde910a37f88322edcfb5dd907a8 # 5.0.0