Update gitlab-codebuild.yml

.github/workflows/gitlab-codebuild.yml

 name: Github to Gitlab CI - Run CodeBuild
 
 env:
+  PR_NUMBER: ${{ github.event.number }}
   GITLAB_TOKEN: ${{ secrets.GITLAB_TOKEN }}
 
 on:
@@ -26,10 +27,10 @@ jobs:
           git config --global user.email "project_14468_bot_3f7d8e1a392afd88ead5f3f3154e809d@noreply.gitlab.com"
           git clone https://isis-codebuild-ci:$GITLAB_TOKEN@code.usgs.gov/astrogeology/isis-codebuild-ci.git
           cd isis-codebuild-ci
-          git checkout -b $BRANCH_NAME
+          git checkout -b $PR_NUMBER
           echo -e "\nenv: \n  shell: bash \n  variables: \n    PR_NUMBER: $PR_NUMBER \n    MERGE_BRANCH: $GITHUB_BASE_REF" >> buildspec.yml
-          git commit -a -m "$BRANCH_NAME"
-          git push origin $BRANCH_NAME --force
+          git commit -a -m "$PR_NUMBER"
+          git push origin $PR_NUMBER --force
           
   comment-bot:
       permissions: write-all