[#24] fix typo to deploy only on master branch (#27)

Author: jmag722

.github/workflows/CI.yml

@@ -34,7 +34,7 @@ jobs:
           name: doc-latest
           path: doc/
   deploy:
-    if: github.ref == 'ref/heads/master'
+    if: github.ref == 'refs/heads/master'
     needs: build-test
 
     # Grant GITHUB_TOKEN the permissions required to make a Pages deployment