Update actions/checkout action to v6

Author: renovate[bot]

.github/workflows/codetests.yml

@@ -9,7 +9,7 @@ jobs:
         os: [ubuntu, macos]
     runs-on: ${{ matrix.os }}-latest
     steps:
-      - uses: actions/checkout@v4 
+      - uses: actions/checkout@v6 
       - uses: actions/setup-go@v5
         with:
           go-version: 'stable'

.github/workflows/release.yml

@@ -12,7 +12,7 @@ jobs:
   release:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
         with:
           fetch-depth: 0
       - name: Import GPG key