Bug 1889033 - Allow warnings in rure. r=emilio

Because we're patching the third-party rure crate, it's considered
first-party, and warnings are turned into errors, but what we really
want is for warnings to be ignored like other third party crates.

Differential Revision: https://phabricator.services.mozilla.com/D206303

third_party/rust/rure/src/lib.rs

@@ -1,3 +1,7 @@
+// This library is patched, this considered first-party. Ignore warnings
+// as if it were third-party.
+#![allow(warnings)]
+
 #[macro_use]
 mod macros;
 mod error;