ci(deps): update actions/checkout action to v6

Author: renovate[bot]

.github/workflows/built_and_test.yml

@@ -73,7 +73,7 @@ jobs:
       && contains(github.repository, 'Kelvindev15/Kotlin2PlantUML')
     steps:
       - name: Checkout
-        uses: actions/checkout@93cb6efe18208431cddfb8368fd83d5badbf9bfd # v5.0.1
+        uses: actions/checkout@1af3b93b6815bc44a9784bd300feb67ff0d1eeb3 # v6.0.0
         with:
           submodules: recursive
       - uses: actions/[email protected]