Remove unused -Wno-implicit-function-declaration.

Change-Id: I611aaeb17f8537c7e801816f6913ac633ef70ddb

Android.bp

diff --git a/Android.bp b/Android.bp
index 16e6374..d032c66 100644
--- a/Android.bp
+++ b/Android.bp
@@ -31,7 +31,6 @@
         "-Werror",
         "-Wno-pointer-arith",
         "-Wno-unused-parameter",
-        "-Wno-implicit-function-declaration",
         "-D_GNU_SOURCE"
     ],
     export_include_dirs: [