chore(deps): bump actions/checkout from 5 to 6

Bumps [actions/checkout](https://github.com/actions/checkout) from 5 to 6.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](https://github.com/actions/checkout/compare/v5...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>

.github/workflows/benchmark.yml

@@ -25,6 +25,6 @@ jobs:
           go-version: 1.24.4
           repository: "${{ github.event.inputs.repository || 'TwiN/gatus' }}"
           ref: "${{ github.event.inputs.ref || 'master' }}"
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - name: Benchmark
         run: go test -bench=. ./storage/store

.github/workflows/publish-custom.yml

@@ -10,7 +10,7 @@ jobs:
     runs-on: ubuntu-latest
     timeout-minutes: 60
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - name: Set up QEMU
         uses: docker/setup-qemu-action@v3
       - name: Set up Docker Buildx

.github/workflows/publish-experimental.yml

@@ -5,7 +5,7 @@ jobs:
     runs-on: ubuntu-latest
     timeout-minutes: 60
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - name: Set up QEMU
         uses: docker/setup-qemu-action@v3
       - name: Set up Docker Buildx

.github/workflows/publish-latest.yml

@@ -13,7 +13,7 @@ jobs:
     if: ${{ (github.event.workflow_run.conclusion == 'success') && (github.event.workflow_run.head_repository.full_name == github.repository) }}
     timeout-minutes: 240
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - name: Set up QEMU
         uses: docker/setup-qemu-action@v3
       - name: Set up Docker Buildx

.github/workflows/publish-release.yml

@@ -8,7 +8,7 @@ jobs:
     runs-on: ubuntu-latest
     timeout-minutes: 240
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - name: Set up QEMU
         uses: docker/setup-qemu-action@v3
       - name: Set up Docker Buildx

.github/workflows/test-ui.yml

@@ -13,6 +13,6 @@ jobs:
     runs-on: ubuntu-latest
     timeout-minutes: 30
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - run: make frontend-install-dependencies
       - run: make frontend-build

.github/workflows/test.yml

@@ -19,7 +19,7 @@ jobs:
       - uses: actions/setup-go@v6
         with:
           go-version: 1.24.4
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - name: Build binary to make sure it works
         run: go build
       - name: Test