Explain Java 8 option warning suppression

Document why only javac's options lint category is disabled for the Kotlin extractor.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: jketema

java/kotlin-extractor/BUILD.bazel

@@ -91,6 +91,7 @@ _component_registrar_service = (
 kt_javac_options(
     name = "javac-options",
     release = "8",
+    # JDK 25 reports Java 8 option warnings; keep them from becoming errors via Kotlin's warn = "error".
     x_lint = ["-options"],
 )