Bump actions/checkout from 4 to 6

Bumps [actions/checkout](https://github.com/actions/checkout) from 4 to 6.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v4...v6)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-version: '6'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

.github/workflows/build.yml

@@ -11,7 +11,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout code
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
         with:
           fetch-depth: 1
 
@@ -37,7 +37,7 @@ jobs:
     steps:
 
       - name: Checkout code
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
         with:
           fetch-depth: 1
 

.github/workflows/nix-action-rocq-9.1.yml

@@ -9,7 +9,7 @@ jobs:
         github.sha }}\" >> $GITHUB_ENV\nelse\n  echo \"target_commit=${{ github.event.pull_request.head.sha
         }}\" >> $GITHUB_ENV\nfi\n"
     - name: Git checkout
-      uses: actions/checkout@v4
+      uses: actions/checkout@v6
       with:
         fetch-depth: 0
         ref: ${{ env.target_commit }}
@@ -23,7 +23,7 @@ jobs:
         }}\" >> $GITHUB_ENV\n  else\n    echo \"tested_commit=$merge_commit\" >> $GITHUB_ENV\n\
         \  fi\nfi\n"
     - name: Git checkout
-      uses: actions/checkout@v4
+      uses: actions/checkout@v6
       with:
         fetch-depth: 0
         ref: ${{ env.tested_commit }}
@@ -68,7 +68,7 @@ jobs:
         github.sha }}\" >> $GITHUB_ENV\nelse\n  echo \"target_commit=${{ github.event.pull_request.head.sha
         }}\" >> $GITHUB_ENV\nfi\n"
     - name: Git checkout
-      uses: actions/checkout@v4
+      uses: actions/checkout@v6
       with:
         fetch-depth: 0
         ref: ${{ env.target_commit }}
@@ -82,7 +82,7 @@ jobs:
         }}\" >> $GITHUB_ENV\n  else\n    echo \"tested_commit=$merge_commit\" >> $GITHUB_ENV\n\
         \  fi\nfi\n"
     - name: Git checkout
-      uses: actions/checkout@v4
+      uses: actions/checkout@v6
       with:
         fetch-depth: 0
         ref: ${{ env.tested_commit }}
@@ -150,7 +150,7 @@ jobs:
         github.sha }}\" >> $GITHUB_ENV\nelse\n  echo \"target_commit=${{ github.event.pull_request.head.sha
         }}\" >> $GITHUB_ENV\nfi\n"
     - name: Git checkout
-      uses: actions/checkout@v4
+      uses: actions/checkout@v6
       with:
         fetch-depth: 0
         ref: ${{ env.target_commit }}
@@ -164,7 +164,7 @@ jobs:
         }}\" >> $GITHUB_ENV\n  else\n    echo \"tested_commit=$merge_commit\" >> $GITHUB_ENV\n\
         \  fi\nfi\n"
     - name: Git checkout
-      uses: actions/checkout@v4
+      uses: actions/checkout@v6
       with:
         fetch-depth: 0
         ref: ${{ env.tested_commit }}