Update actions/checkout action to v5

Author: renovate[bot]

.github/workflows/publishing.yml

@@ -16,7 +16,7 @@ jobs:
           go-version: 1.25
 
       - name: Checkout
-        uses: actions/checkout@v4
+        uses: actions/checkout@v5
 
       - name: Test
         run: go test -v -race

.github/workflows/testing.yml

@@ -16,7 +16,7 @@ jobs:
           go-version: 1.25
 
       - name: Checkout
-        uses: actions/checkout@v4
+        uses: actions/checkout@v5
 
       - name: Test
         run: go test -v -race