Merge #5916

5916: fix import on mastersrv r=heinrich5991 a=edg-l

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## Checklist

- [ ] Tested the change ingame
- [ ] Provided screenshots if it is a visual change
- [ ] Tested in combination with possibly related configuration options
- [ ] Written a unit test (especially base/) or added coverage to integration test
- [ ] Considered possible null pointers and out of bounds array indexing
- [ ] Changed no physics that affect existing maps
- [ ] Tested the change with [ASan+UBSan or valgrind's memcheck](https://github.com/ddnet/ddnet/#using-addresssanitizer--undefinedbehavioursanitizer-or-valgrinds-memcheck) (optional)


Co-authored-by: Edgar Luque <git@edgarluque.com>

src/mastersrv/src/addr.rs

@@ -272,6 +272,7 @@ impl<'de> serde::Deserialize<'de> for RegisterAddr {
 mod test {
     use super::Addr;
     use super::Protocol;
+    use super::RegisterAddr;
     use std::net::IpAddr;
     use std::str::FromStr;