net/http/httptrace: fix doc typo

Change-Id: I919d9c3968c0fcd33774e714f22182504790bd01
Reviewed-on: https://go-review.googlesource.com/c/go/+/284143
Reviewed-by: Ian Lance Taylor <[email protected]>
Reviewed-by: Daniel Martí <[email protected]>
Trust: Daniel Martí <[email protected]>

Author: rhcarvalho

src/net/http/httptrace/trace.go

@@ -127,7 +127,7 @@ type ClientTrace struct {
 
 	// ConnectDone is called when a new connection's Dial
 	// completes. The provided err indicates whether the
-	// connection completedly successfully.
+	// connection completed successfully.
 	// If net.Dialer.DualStack ("Happy Eyeballs") support is
 	// enabled, this may be called multiple times.
 	ConnectDone func(network, addr string, err error)