all: run gofmt -s on source code

Per the description, the "-s" file issues slight simplifications to
the source code.

Change-Id: I77395d763f5eafb48653902dcedfa56b150b2d67
Reviewed-on: https://go-review.googlesource.com/80138
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

sha3/sha3_test.go

@@ -202,7 +202,7 @@ func TestSqueezing(t *testing.T) {
 			d1 := newShakeHash()
 			d1.Write([]byte(testString))
 			var multiple []byte
-			for _ = range ref {
+			for range ref {
 				one := make([]byte, 1)
 				d1.Read(one)
 				multiple = append(multiple, one...)