fix spell (#1314)

diff --git a/clientconn.go b/clientconn.go
index 7565573..902d7d5 100644
--- a/clientconn.go
+++ b/clientconn.go
@@ -487,7 +487,7 @@
 	mu    sync.RWMutex
 	sc    ServiceConfig
 	conns map[Address]*addrConn
-	// Keepalive parameter can be udated if a GoAway is received.
+	// Keepalive parameter can be updated if a GoAway is received.
 	mkp keepalive.ClientParameters
 }