Update actions/checkout action to v4 (#24)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

.github/workflows/auto-readme.yml

@@ -24,7 +24,7 @@ jobs:
   update:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
 
       - name: Find default branch name
         id: defaultBranch

.github/workflows/setup-test.yml

@@ -21,7 +21,7 @@ jobs:
         run: echo "Do setup"
 
       - name: Checkout
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
 
       - uses: ./
         id: writer

.github/workflows/test-negative.yml

@@ -18,7 +18,7 @@ jobs:
         run: echo "Do setup"
 
       - name: Checkout
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
 
       - uses: ./
         id: writer

.github/workflows/test-non-matrix.yml

@@ -20,7 +20,7 @@ jobs:
     needs: [setup]
     steps:
       - name: Checkout
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
 
       - uses: ./
         id: current

.github/workflows/test-positive.yml

@@ -18,7 +18,7 @@ jobs:
         run: echo "Do setup"
 
       - name: Checkout
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
 
       - uses: ./
         id: writer

.github/workflows/test-special-chars.yml

@@ -25,7 +25,7 @@ jobs:
         run: echo "Do setup"
 
       - name: Checkout
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
 
       - uses: ./
         id: writer

.github/workflows/test-validation.yml

@@ -23,7 +23,7 @@ jobs:
     needs: [setup]
     steps:
       - name: Checkout
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
 
       - uses: ./
         id: current