Target Java 21 by default

Bug: 342332820
Test: TH
Change-Id: I3d440c79231cc470013610c8b3ec95a0b4a0cb6a
diff --git a/java/java.go b/java/java.go
index 53b3481..e95bd1b 100644
--- a/java/java.go
+++ b/java/java.go
@@ -606,10 +606,8 @@
 	} else if ctx.Device() {
 		return defaultJavaLanguageVersion(ctx, sdkContext.SdkVersion(ctx))
 	} else if ctx.Config().TargetsJava21() {
-		// Temporary experimental flag to be able to try and build with
-		// java version 21 options.  The flag, if used, just sets Java
-		// 21 as the default version, leaving any components that
-		// target an older version intact.
+		// Build flag that controls whether Java 21 is used as the default
+		// target version, or Java 17.
 		return JAVA_VERSION_21
 	} else {
 		return JAVA_VERSION_17