Remove @pietern from CODEOWNERS (#4093)

Author: pietern

.github/CODEOWNERS

@@ -7,5 +7,5 @@
 /cmd/workspace/apps/      @databricks/eng-app-devex
 /libs/apps/               @databricks/eng-app-devex
 /acceptance/apps/         @databricks/eng-app-devex
-/experimental/aitools/    @databricks/eng-app-devex @pietern @lennartkats-db
-/experimental/apps-mcp/   @databricks/eng-app-devex @pietern @lennartkats-db
+/experimental/aitools/    @databricks/eng-app-devex @lennartkats-db
+/experimental/apps-mcp/   @databricks/eng-app-devex @lennartkats-db