Bump actions/checkout from 3 to 6

Bumps [actions/checkout](https://github.com/actions/checkout) from 3 to 6.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v3...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] <[email protected]>

Author: dependabot[bot]

.github/workflows/docker.yml

@@ -31,7 +31,7 @@ jobs:
         df -h
       
     - name: Checkout repo
-      uses: actions/checkout@v3
+      uses: actions/checkout@v6
       with:
         fetch-depth: 0
 

.github/workflows/pr.yml

@@ -33,7 +33,7 @@ jobs:
       CARGO_NET_GIT_FETCH_WITH_CLI: "true"
     steps:
       - name: Checkout sources
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
 
       - name: Setup Runs-On Runner
         uses: ./.github/actions/runs-on
@@ -105,7 +105,7 @@ jobs:
       CARGO_NET_GIT_FETCH_WITH_CLI: "true"
     steps:
       - name: Checkout sources
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
 
       # - name: Setup Self-Hosted Runner
       #   uses: ./.github/actions/self-hosted
@@ -176,7 +176,7 @@ jobs:
       CARGO_NET_GIT_FETCH_WITH_CLI: "true"
     steps:
       - name: Checkout sources
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
 
       # Commented out because the latency of the docker buildx cache is high enough 
       # with the EC2 builder that it's a wash.  Can be added back in if the toolchain gets complex.