fix: single quotes in workflow

Author: leonhma

.github/workflows/ci.yml

@@ -7,7 +7,7 @@ on:
 jobs:
   build:
     runs-on: ubuntu-latest
-    if: github.ref_type == "branch"
+    if: github.ref_type == 'branch'
     steps:
       - uses: actions/checkout@v2