Bump actions/setup-node from 5 to 6

Bumps [actions/setup-node](https://github.com/actions/setup-node) from 5 to 6.
- [Release notes](https://github.com/actions/setup-node/releases)
- [Commits](actions/setup-node@v5...v6)

---
updated-dependencies:
- dependency-name: actions/setup-node
  dependency-version: '6'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

.github/workflows/generate-mindmap.yml

@@ -29,7 +29,7 @@ jobs:
     steps:
     - uses: actions/checkout@v5
     - name: Use Node.js
-      uses: actions/setup-node@v5
+      uses: actions/setup-node@v6
       with:
         node-version: 20
         cache: 'npm'

.github/workflows/markdownlint.yml

@@ -22,7 +22,7 @@ jobs:
     steps:
     - uses: actions/checkout@v5
     - name: Use Node.js
-      uses: actions/setup-node@v5
+      uses: actions/setup-node@v6
       with:
         node-version: 20
     - name: Run Markdownlint