[tests] fixed a test that fails due to, of all things, a javac bug.

test/pretty/resource/before/ThisParameter.java

@@ -1,3 +1,4 @@
+// version 9: the 'this' param option exists in java8, but is bugged, in that annotations are not allowed on them, even without a @Target. The only purpose of the this param is annotations, so, boy, isn't that a punch in the face?
 import java.lang.annotation.ElementType;
 import java.lang.annotation.Retention;
 import java.lang.annotation.RetentionPolicy;