Update GitHub Actions checkout to v4 (#136)

Author: HonKLam

.github/workflows/godot-ci.yml

@@ -14,7 +14,7 @@ jobs:
       image: barichello/godot-ci:4.2.1
     steps:
       - name: Checkout
-        uses: actions/checkout@v2
+        uses: actions/checkout@v4
         with:
           lfs: true
       - name: Setup
@@ -39,7 +39,7 @@ jobs:
       image: barichello/godot-ci:4.2.1
     steps:
       - name: Checkout
-        uses: actions/checkout@v2
+        uses: actions/checkout@v4
         with:
           lfs: true
       - name: Setup
@@ -64,7 +64,7 @@ jobs:
       image: barichello/godot-ci:4.2.1
     steps:
       - name: Checkout
-        uses: actions/checkout@v2
+        uses: actions/checkout@v4
         with:
           lfs: true
       - name: Setup
@@ -97,7 +97,7 @@ jobs:
       image: barichello/godot-ci:4.2.1
     steps:
       - name: Checkout
-        uses: actions/checkout@v2
+        uses: actions/checkout@v4
         with:
           lfs: true
       - name: Setup