Fix Rust 1.99 lint for generated service traits

clients/rust/src/generated.rs

@@ -14,6 +14,9 @@ pub mod mxaccess_gateway {
     /// gateway to language clients.
     pub mod v1 {
         #![allow(clippy::large_enum_variant, clippy::result_large_err)]
+        // tonic's generated server traits use async_trait, whose expansion adds
+        // redundant must_use attributes to Future returns under Rust 1.99.
+        #![allow(clippy::double_must_use)]
 
         tonic::include_proto!("mxaccess_gateway.v1");
     }
@@ -36,6 +39,9 @@ pub mod galaxy_repository {
     /// discovery and deploy-event watch RPCs.
     pub mod v1 {
         #![allow(clippy::large_enum_variant, clippy::result_large_err)]
+        // tonic's generated server traits use async_trait, whose expansion adds
+        // redundant must_use attributes to Future returns under Rust 1.99.
+        #![allow(clippy::double_must_use)]
 
         tonic::include_proto!("galaxy_repository.v1");
     }