Update actions/checkout action to v6

Author: renovate[bot]

.github/workflows/frontend-check.yml

@@ -9,7 +9,7 @@ jobs:
     name: Check
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - uses: actions/setup-node@v4
       - run: npm install
       - name: Bundle OpenAPI & Build Redocly Docs

.github/workflows/frontend-publish-npm-gh.yml

@@ -9,7 +9,7 @@ jobs:
     name: Publish to NPM & Github Pages
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - uses: actions/setup-node@v4
         with:
           registry-url: "https://registry.npmjs.org"

.github/workflows/release-erlang.yml

@@ -13,7 +13,7 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - uses: actions/setup-node@v4
 
       - name: Setup swagger-codegen

.github/workflows/release.yml

@@ -9,7 +9,7 @@ jobs:
   release:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - uses: actions/setup-node@v4
         with:
           node-version: '20'