s/IMPL_HEADER/IMPL_INTERFACE/g

More appropriate name for this enum constant now that they are defined
in the interface source files.

Test: hidl_test
Change-Id: Ice531adb797c3213a2da18421b7e97fcfc888da3
diff --git a/generateJava.cpp b/generateJava.cpp
index 0694a82..36cef4e 100644
--- a/generateJava.cpp
+++ b/generateJava.cpp
@@ -479,7 +479,7 @@
             << ") {\n";
 
         out.indent();
-        method->javaImpl(IMPL_HEADER, out);
+        method->javaImpl(IMPL_INTERFACE, out);
         out.unindent();
         out << "\n}\n\n";
     }