archive/zip: remove unnecessary words in (*Writer).Close docs

Fixes #25599

Change-Id: I19ac3463682f662515feaf4c6132f55c12ba5386
Reviewed-on: https://go-review.googlesource.com/115618Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/archive/zip/writer.go

@@ -72,7 +72,7 @@ func (w *Writer) SetComment(comment string) error {
 }
 
 // Close finishes writing the zip file by writing the central directory.
-// It does not (and cannot) close the underlying writer.
+// It does not close the underlying writer.
 func (w *Writer) Close() error {
 	if w.last != nil && !w.last.closed {
 		if err := w.last.close(); err != nil {