Bump actions/checkout from 2 to 4

Bumps [actions/checkout](https://github.com/actions/checkout) from 2 to 4.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v2...v4)

---
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/R-CMD-as-cran-check.yaml

@@ -26,7 +26,7 @@ jobs:
       NOT_CRAN: false
 
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
 
       - uses: r-lib/actions/setup-pandoc@v2
 

.github/workflows/R-CMD-check.yaml

@@ -45,7 +45,7 @@ jobs:
       NOT_CRAN: true
 
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
 
       - name: Install cmdstan Linux system dependencies
         if: runner.os == 'Linux'

.github/workflows/lint-only-changed-files.yaml

@@ -15,7 +15,7 @@ jobs:
     env:
       GITHUB_PAT: ${{ secrets.GITHUB_TOKEN }}
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
 
       - uses: r-lib/actions/setup-r@v2
 

.github/workflows/pkgdown.yaml

@@ -17,7 +17,7 @@ jobs:
     env:
       GITHUB_PAT: ${{ secrets.GITHUB_TOKEN }}
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
 
       - uses: r-lib/actions/setup-pandoc@v2
 

.github/workflows/pr-commands.yaml

@@ -16,7 +16,7 @@ jobs:
     env:
       GITHUB_PAT: ${{ secrets.GITHUB_TOKEN }}
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
       - uses: r-lib/actions/pr-fetch@v1
         with:
           repo-token: ${{ secrets.GITHUB_TOKEN }}
@@ -42,7 +42,7 @@ jobs:
     env:
       GITHUB_PAT: ${{ secrets.GITHUB_TOKEN }}
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
       - uses: r-lib/actions/pr-fetch@v1
         with:
           repo-token: ${{ secrets.GITHUB_TOKEN }}

.github/workflows/render-readme.yaml

@@ -10,7 +10,7 @@ jobs:
     env:
       GITHUB_PAT: ${{ secrets.GITHUB_TOKEN }}
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
 
       - uses: r-lib/actions/setup-pandoc@v2
 

.github/workflows/test-coverage.yaml

@@ -18,7 +18,7 @@ jobs:
       NOT_CRAN: true
 
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
 
       - uses: r-lib/actions/setup-r@v2
         with:

.github/workflows/touchstone-receive.yaml

@@ -22,7 +22,7 @@ jobs:
       config: ${{ steps.read_touchstone_config.outputs.config }}
     steps:
       - name: Checkout repo
-        uses: actions/checkout@v2
+        uses: actions/checkout@v4
         with:
           fetch-depth: 0
 

.github/workflows/update-citation-cff.yaml

@@ -22,7 +22,7 @@ jobs:
     env:
       GITHUB_PAT: ${{ secrets.GITHUB_TOKEN }}
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: r-lib/actions/setup-r@v2
       - uses: r-lib/actions/setup-r-dependencies@v2
         with: