Remove Java21InputAstVisitor until JDK 21 is used

Bug: 313924276
Test: m
Change-Id: I13c1b6dd1eb2fbb9ec57784422e2eebd6c0b7f0d

Android.bp

diff --git a/Android.bp b/Android.bp
index 8df1c08..0c267f9 100644
--- a/Android.bp
+++ b/Android.bp
@@ -50,6 +50,7 @@
     exclude_srcs: [
         ":google_java_format_main_srcs",
         "core/src/main/java/com/google/googlejavaformat/java/GoogleJavaFormatToolProvider.java",
+        "core/src/main/java/com/google/googlejavaformat/java/java21/Java21InputAstVisitor.java",
     ],
     libs: [
         "error_prone_annotations",