Suppress only javac option warnings in the Kotlin extractor

Use -Xlint:-options for the Java 8 compatibility warnings instead of disabling all javac warnings. Other warnings retain the warnings-as-errors behavior inherited from Kotlin.

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

Author: jketema

java/kotlin-extractor/BUILD.bazel

@@ -91,8 +91,7 @@ _component_registrar_service = (
 kt_javac_options(
     name = "javac-options",
     release = "8",
-    # Keep javac warnings separate from the Kotlin compiler's warn = "error".
-    warn = "off",
+    x_lint = ["-options"],
 )
 
 [