os: remove ineffective else branch

Change-Id: Ic9cf871d862aec54ab8f491b8bc8d2820aecc875
Reviewed-on: https://go-review.googlesource.com/c/go/+/582497
Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>
Auto-Submit: Quim Muntal <quimmuntal@gmail.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>

src/os/path_windows.go

@@ -236,8 +236,6 @@ func addExtendedPrefix(path string) string {
 		if n <= uint32(len(buf)-len(prefix)) {
 			buf = buf[:n+uint32(len(prefix))]
 			break
-		} else {
-			continue
 		}
 	}
 	if isUNC {