Upgrade version of actions/checkout action in CI workflow

The "actions/checkout" action version has been updated from v3 to v4 in the CI workflow file (.github/workflows/ci.yml). This change applies to multiple steps in the file, making the workflow use the more recent version of the action during the Checkout process.

.github/workflows/ci.yml

@@ -10,7 +10,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: "Checkout"
-        uses: "actions/checkout@v3"
+        uses: "actions/checkout@v4"
         with:
           fetch-depth: 2
 
@@ -52,7 +52,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: "Checkout"
-        uses: "actions/checkout@v3"
+        uses: "actions/checkout@v4"
         with:
           fetch-depth: 2
 
@@ -94,7 +94,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: "Checkout"
-        uses: "actions/checkout@v3"
+        uses: "actions/checkout@v4"
         with:
           fetch-depth: 2