workflows: use v4 of actions/checkout

.github/workflows/format.yml

@@ -8,7 +8,7 @@ jobs:
     if: github.repository != 'jMonkeyEngine/jmonkeyengine'
     steps:
       - name: Checkout
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
         with:
           fetch-depth: 0   
       - name: Prettify code

.github/workflows/main.yml

@@ -65,7 +65,7 @@ jobs:
 
     steps:
       - name: Clone the repo
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
         with:
           fetch-depth: 1
       - name: Validate the Gradle wrapper
@@ -108,7 +108,7 @@ jobs:
 
     steps:
       - name: Clone the repo
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
         with:
           fetch-depth: 1
 
@@ -301,7 +301,7 @@ jobs:
 
       # We need to clone everything again for uploadToMaven.sh ...
       - name: Clone the repo
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
         with:
           fetch-depth: 1
 
@@ -345,7 +345,7 @@ jobs:
 
       # We need to clone everything again for uploadToMaven.sh ...
       - name: Clone the repo
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
         with:
           fetch-depth: 1