Update dependency ruby to v4

Author: renovate[bot]

.github/workflows/test_runner.yml

@@ -37,7 +37,7 @@ jobs:
       - uses: actions/checkout@v4
       - uses: ruby/setup-ruby@v1
         with:
-          ruby-version: 2.6
+          ruby-version: 4.0.2
       - run: |
           gem install arduino_ci
           arduino_ci.rb --skip-examples-compilation