cmd/compile/internal/ssa: ignore error from second call to MatchString in test

Change-Id: I714612b41facc8d1ec22974e8aaf2a5a3592e8f5
GitHub-Last-Rev: a0b3917e45bc1d24590e9c9cb3550da4c4008c49
GitHub-Pull-Request: golang/go#29998
Reviewed-on: https://go-review.googlesource.com/c/160422
Run-TryBot: Bryan C. Mills <bcmills@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>

src/cmd/compile/internal/ssa/debug_test.go

@@ -934,7 +934,8 @@ func expect(want string, got tstring) {
 		if match {
 			return
 		}
-		match, err = regexp.MatchString(want, got.e)
+		// Ignore error as we have already checked for it before
+		match, _ = regexp.MatchString(want, got.e)
 		if match {
 			return
 		}