Stop exporting private "zutil.h" implementation detail.

Test: builds
Change-Id: Ia6be00bf3c77b3db5717717d2604e616e2ea3eb8
diff --git a/Android.bp b/Android.bp
index da01daf..395e237 100644
--- a/Android.bp
+++ b/Android.bp
@@ -96,7 +96,6 @@
 //     srcs: [
 //         "src/zconf.h",
 //         "src/zlib.h",
-//         "src/zutil.h",
 //     ],
 //     license: "NOTICE",
 // }
diff --git a/zutil.h b/zutil.h
deleted file mode 120000
index 12e5986..0000000
--- a/zutil.h
+++ /dev/null
@@ -1 +0,0 @@
-src/zutil.h
\ No newline at end of file