Update unit test to reflect changes to warning text.

Author: pnkfelix

src/test/compile-fail/lint-no-drop-on-repr-extern.rs

@@ -21,10 +21,10 @@
 struct B { x: Box<i8> }
 
 #[repr(C)] struct C { x: Box<i8> }
-//~^ ERROR The `#[repr(C)]` attribute is attached here
+//~^ ERROR the `#[repr(C)]` attribute is attached here
 
 impl Drop for C { fn drop(&mut self) { } }
-//~^ ERROR Structs with `#[repr(C)]` attribute that implement Drop have extra hidden state
+//~^ ERROR implementing Drop adds hidden state to types, possibly conflicting with `#[repr(C)]`
 
 #[unsafe_no_drop_flag]
 #[repr(C)] struct D { x: Box<i8> }