Bump actions/checkout to v4 in CI

Author: flashcode

.github/workflows/ci.yml

@@ -37,7 +37,7 @@ jobs:
 
     steps:
 
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
 
       - name: Install dependencies
         run: |
@@ -93,7 +93,7 @@ jobs:
 
     steps:
 
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
 
       - name: Install dependencies
         run: |
@@ -135,7 +135,7 @@ jobs:
 
     steps:
 
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
 
       - name: Install dependencies
         run: |