Bump actions/checkout from 3.6.0 to 4.0.0

Bumps [actions/checkout](https://github.com/actions/checkout) from 3.6.0 to 4.0.0.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v3.6.0...v4.0.0)

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

Signed-off-by: dependabot[bot] <[email protected]>

.github/workflows/integration.yml

@@ -21,7 +21,7 @@ jobs:
 
     steps:
     - name: Check out VERDICT source
-      uses: actions/checkout@v3.6.0
+      uses: actions/checkout@v4.0.0
 
     - name: Set up GraphViz
       uses: ts-graphviz/setup-graphviz@v1

.github/workflows/main.yml

@@ -26,7 +26,7 @@ jobs:
 
     steps:
     - name: Check out VERDICT source
-      uses: actions/checkout@v3.6.0
+      uses: actions/checkout@v4.0.0
 
     - name: Set up OCaml
       uses: ocaml/[email protected]
@@ -85,7 +85,7 @@ jobs:
 
     - name: Check out VERDICT-update-sites
       if: runner.os == 'Linux'
-      uses: actions/checkout@v3.6.0
+      uses: actions/checkout@v4.0.0
       with:
         repository: ge-high-assurance/VERDICT-update-sites
         token: ${{ secrets.CI_PAT }}

.github/workflows/release.yml

@@ -22,11 +22,11 @@ jobs:
 
     steps:
     - name: Check out VERDICT source
-      uses: actions/checkout@v3.6.0
+      uses: actions/checkout@v4.0.0
 
     - name: Check out kind2 source
       if: runner.os == 'macOS'
-      uses: actions/checkout@v3.6.0
+      uses: actions/checkout@v4.0.0
       with:
         repository: kind2-mc/kind2
         path: tools/verdict-back-ends/kind2
@@ -92,7 +92,7 @@ jobs:
 
     steps:
     - name: Check out VERDICT source
-      uses: actions/checkout@v3.6.0
+      uses: actions/checkout@v4.0.0
 
     - name: Set up GraphViz
       uses: ts-graphviz/setup-graphviz@v1
@@ -164,7 +164,7 @@ jobs:
           gehighassurance/verdict:${{ github.event.release.tag_name }}
 
     - name: Check out VERDICT-update-sites
-      uses: actions/checkout@v3.6.0
+      uses: actions/checkout@v4.0.0
       with:
         repository: ge-high-assurance/VERDICT-update-sites
         token: ${{ secrets.CI_PAT }}