Dismiss some compile-time warnings

The `unused_results` lint was complaining that the results of inserting into a `MockUsers` object weren't being inspected. These are mock users, so all that would be returned is `None` to indicate that they weren't already in the table -- they're fine to ignore! So, suppress the warnings for those two testing modules.

src/output/details.rs

@@ -771,6 +771,7 @@ pub mod test {
     // Metadata struct, which is what I was doing before!
 
     mod users {
+        #![allow(unused_results)]
         use super::*;
 
         #[test]
@@ -833,6 +834,7 @@ pub mod test {
     }
 
     mod groups {
+        #![allow(unused_results)]
         use super::*;
 
         #[test]