THRIFT-5600: upgrade rust toolchain to 1.61 and edition 2021
THRIFT-5606: Wrong indent for const double
Client: rs
Patch: Ommy Zhang <tdxdxoz@gmail.com>

This closes #2634
diff --git a/lib/rs/src/server/multiplexed.rs b/lib/rs/src/server/multiplexed.rs
index 8331d91..b447d38 100644
--- a/lib/rs/src/server/multiplexed.rs
+++ b/lib/rs/src/server/multiplexed.rs
@@ -170,8 +170,7 @@
             let (_, svc_call) = svc_call.split_at(1); // remove colon from service call name
             (Some(svc_name), svc_call)
         })
-        .or_else(|| Some((None, ident_name)))
-        .unwrap()
+        .unwrap_or((None, ident_name))
 }
 
 fn missing_processor_message(svc_name: Option<&str>) -> String {