net/http: fix typo in Transport docs

Author: veecore

src/net/http/transport.go

@@ -87,7 +87,7 @@ const DefaultMaxIdleConnsPerHost = 2
 // ClientTrace.Got1xxResponse.
 //
 // Transport only retries a request upon encountering a network error
-// if the connection has been already been used successfully and if the
+// if the connection has already been used successfully and if the
 // request is idempotent and either has no body or has its [Request.GetBody]
 // defined. HTTP requests are considered idempotent if they have HTTP methods
 // GET, HEAD, OPTIONS, or TRACE; or if their [Header] map contains an