Bug 1793882 - Don't "return" c_void in NS_NewHashPropertyBag declarat…

…ion. r=emilio

A function that "returns" c_void in rust ends up transposed as returning
a bool (i1) at the LLVM-IR level, compared to the definition in C/C++
returning a void at the LLVM-IR level.

Differential Revision: https://phabricator.services.mozilla.com/D158722

storage/variant/src/bag.rs

@@ -13,7 +13,7 @@ use xpcom::{
 use crate::{NsIVariantExt, VariantType};
 
 extern "C" {
-    fn NS_NewHashPropertyBag(bag: *mut *const nsIWritablePropertyBag) -> libc::c_void;
+    fn NS_NewHashPropertyBag(bag: *mut *const nsIWritablePropertyBag);
 }
 
 /// A hash property bag backed by storage variant values.