bufio: Remove unneeded error initialization

The default value for error is nil so there is no need to assign this
value here.

Change-Id: I4714ef7607996ccbf91b704390e1d1d39ee3847b
Reviewed-on: https://go-review.googlesource.com/12355Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/bufio/bufio.go

@@ -400,7 +400,6 @@ func (b *Reader) ReadBytes(delim byte) (line []byte, err error) {
 	// accumulating full buffers.
 	var frag []byte
 	var full [][]byte
-	err = nil
 
 	for {
 		var e error