go/internal/gcimporter: remove unused assignment

Change-Id: I0b19731a46e4e67a7dd503dd133cafc7678760a7
Reviewed-on: https://go-review.googlesource.com/13890Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/go/internal/gcimporter/exportdata.go

@@ -71,7 +71,7 @@ func FindExportData(r *bufio.Reader) (err error) {
 				size -= n
 			}
 
-			if name, size, err = readGopackHeader(r); err != nil {
+			if name, _, err = readGopackHeader(r); err != nil {
 				return
 			}
 		}