Modified checkout action from actions/checkout@v2 to actions/checkout@v3

Signed-off-by: SungHyeon Oh <[email protected]>

.github/workflows/ros-ci.yml

@@ -37,7 +37,7 @@ jobs:
       - name: Setup directories
         run: mkdir -p ros_ws/src
       - name: checkout
-        uses: actions/checkout@v2
+        uses: actions/checkout@v3
         with:
           path: ros_ws/src
       - name: Setup ROS environment