Update actions/checkout action to v6

Author: renovate[bot]

.github/workflows/build.yaml

@@ -18,7 +18,7 @@ jobs:
     runs-on: ubuntu-latest
     name: Build main TTFs
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - name: Set up latest harfbuzz
         uses: notofonts/install-harfbuzz-action@main
       - name: Set up Python
@@ -55,7 +55,7 @@ jobs:
     runs-on: ubuntu-latest
     needs: build-all
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - name: Download font build zip
         uses: actions/download-artifact@v4
         with:
@@ -91,7 +91,7 @@ jobs:
     runs-on: ubuntu-latest
     needs: build-all
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - name: Download font build zip
         uses: actions/download-artifact@v4
         with:
@@ -125,7 +125,7 @@ jobs:
     runs-on: ubuntu-latest
     needs: build-all
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - name: Download font build zip
         uses: actions/download-artifact@v4
         with:
@@ -166,7 +166,7 @@ jobs:
       - proof
       - regression
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - name: Download font zip
         uses: actions/download-artifact@v4
         with:
@@ -249,7 +249,7 @@ jobs:
       config_file: ${{ steps.check_tag.outputs.config_file }}
       family: ${{ steps.check_tag.outputs.family }}
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - name: Set up Python
         uses: actions/setup-python@v5
         with:
@@ -328,13 +328,13 @@ jobs:
             echo "::error file=sources/config.yaml,title=USER_GITHUB_TOKEN was not set in repository secrets::Generate a personal access token with a repo scope by visiting https://github.com/settings/tokens/new and add it to an environment secret called USER_GITHUB_TOKEN in an environment called 'googlefonts' by going to $GITHUB_SERVER_URL/$GITHUB_REPOSITORY/settings/secrets/actions";
             exit 1
           fi
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - name: Set up Python
         uses: actions/setup-python@v5
         with:
           python-version: "3.11"
       - run: pip3 install 'git+https://github.com/googlefonts/gftools#egg=gftools'
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
         name: Check out Google Fonts repository
         with:
           fetch-depth: 0