chore(deps): update actions/checkout action to v6

Author: renovate[bot]

.github/workflows/buildifier.yaml

@@ -15,6 +15,6 @@ jobs:
     check:
         runs-on: ubuntu-latest
         steps:
-            - uses: actions/checkout@v5
+            - uses: actions/checkout@v6
             - name: buildifier
               run: bazel run --enable_bzlmod //:buildifier.check

.github/workflows/ci.yaml

@@ -22,7 +22,7 @@ jobs:
     matrix-prep:
         runs-on: ubuntu-latest
         steps:
-            - uses: actions/checkout@v5
+            - uses: actions/checkout@v6
             - id: bazel-version
               name: Prepare 'bazel-version' matrix axis
               run: |
@@ -249,7 +249,7 @@ jobs:
         # Steps represent a sequence of tasks that will be executed as part of the job
         steps:
             # Checks-out your repository under github.workspace, so your job can access it
-            - uses: actions/checkout@v5
+            - uses: actions/checkout@v6
 
             # Setup an ssh keypair and github.com in known_hosts for e2e/git_dep_metadata,
             # which exercises fetching a git repository via ssh.

.github/workflows/mirror.yaml

@@ -11,7 +11,7 @@ jobs:
     mirror:
         runs-on: ubuntu-latest
         steps:
-            - uses: actions/checkout@v5
+            - uses: actions/checkout@v6
             - run: |
                   ./npm/private/versions_mirror.sh
                   npx @bazel/buildifier npm/private/versions.bzl

.github/workflows/tag.yaml

@@ -24,7 +24,7 @@ jobs:
             new-tag: ${{ steps.ccv.outputs.new-tag }}
             new-tag-version: ${{steps.ccv.outputs.new-tag-version}}
         steps:
-            - uses: actions/checkout@v5
+            - uses: actions/checkout@v6
               with:
                   # Need enough history to find the prior release tag
                   fetch-depth: 0