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

Author: cq-bot

.github/workflows/gen_coverage_report.yml

@@ -18,7 +18,7 @@ jobs:
       id-token: write
       contents: write
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
         with:
           token: ${{ secrets.GH_CQ_BOT }}
       - name: Set up Go 1.x

.github/workflows/go_mod_tidy_examples.yml

@@ -17,7 +17,7 @@ jobs:
       matrix:
         plugin: [simple_plugin]
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
         with:
           token: ${{ secrets.GH_CQ_BOT }}
       - name: Set up Go 1.x

.github/workflows/lint_golang.yml

@@ -16,7 +16,7 @@ jobs:
     runs-on: ubicloud-standard-8
     timeout-minutes: 10
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - uses: actions/setup-go@v6
         with:
           go-version-file: go.mod

.github/workflows/lint_markdown.yml

@@ -15,7 +15,7 @@ jobs:
     timeout-minutes: 10
     steps:
       - name: Git checkout
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
       - run: |
           venv="$HOME/.local/share/venv"
           python3 -m venv "$venv"
@@ -33,7 +33,7 @@ jobs:
     timeout-minutes: 10
     steps:
       - name: Git checkout
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
       - name: markdownlint-cli
         uses: nosborn/[email protected]
         with:

.github/workflows/unittest.yml

@@ -19,7 +19,7 @@ jobs:
     timeout-minutes: 15
     steps:
       - name: Check out code into the Go module directory
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
       - name: Set up Go 1.x
         uses: actions/setup-go@v6
         with: