Update: action yml 파일 오타 수정

Author: taenguree

.github/workflows/main.yml

@@ -39,7 +39,7 @@ jobs:
         path: |
           ~/.gradle/caches
           ~/.gradle/wrapper
-        key: ${{ runner.os }}-gradle-${{ github.ref_name }-${{ hashFiles('**/*.gradle*', '**/gradle-wrapper.properties') }}
+        key: ${{ runner.os }}-gradle-${{ github.ref_name }}-${{ hashFiles('**/*.gradle*', '**/gradle-wrapper.properties') }}
         restore-keys: |
           ${{ runner.os }}-gradle-