transform: fix %q verb use with wrong type

Caught early by the improved vet check gated behind the 1.26 language
version combined with a tiplang builder that tests with 1.26 language
version.

Change-Id: If22c0f81d35d7266f05bf5481439db46ea889b25
Cq-Include-Trybots: luci.golang.try:x_text-gotip-linux-amd64-tiplang
Reviewed-on: https://go-review.googlesource.com/c/text/+/725061
Auto-Submit: Alan Donovan <adonovan@google.com>
Auto-Submit: Dmitri Shuralyov <dmitshur@golang.org>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Reviewed-by: Alan Donovan <adonovan@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Commit-Queue: Alan Donovan <adonovan@google.com>

Author: dmitshur

transform/transform_test.go

@@ -733,7 +733,7 @@ func TestDiscard(t *testing.T) {
 	for i, tc := range testCases {
 		nDst, nSrc, err := Discard.Transform(make([]byte, tc.dstSize), []byte(tc.str), true)
 		if nDst != 0 || nSrc != len(tc.str) || err != nil {
-			t.Errorf("%d:\ngot %q, %d, %v\nwant 0, %d, nil", i, nDst, nSrc, err, len(tc.str))
+			t.Errorf("%d:\ngot %d, %d, %v\nwant 0, %d, nil", i, nDst, nSrc, err, len(tc.str))
 		}
 	}
 }