Remove deny_warnings attribute

Test: cd external/rust/crates; mma
Change-Id: Id4c5dc64e315203e52a1abcf853f777bcc09590f
diff --git a/Android.bp b/Android.bp
index bd977c4..8d0a51d 100644
--- a/Android.bp
+++ b/Android.bp
@@ -2,7 +2,6 @@
 
 rust_library_host_rlib {
     name: "libclang_sys",
-    deny_warnings: false,
     crate_name: "clang_sys",
     srcs: ["src/lib.rs"],
     edition: "2015",