adjust newMember var to use known pattern

Our automated build step currently breaks on this test.  Looking at the
other tests in this file that also use newMember, it looks like they're
using a slightly different call, that does not specify ID and Algo (as
these are what's causing the error).

roomdb/sqlite/invites_test.go

@@ -165,7 +165,10 @@ func TestInvites_BypassInvitestToken(t *testing.T) {
 	tr := repo.New(testRepo)
 
 	// fake feed for testing, looks ok at least
-	newMember := refs.FeedRef{ID: bytes.Repeat([]byte("acab"), 8), Algo: refs.RefAlgoFeedSSB1}
+	newMember, err := refs.NewFeedRefFromBytes(bytes.Repeat([]byte("acab"), 8), refs.RefAlgoFeedSSB1)
+	if err != nil {
+		t.Error(err)
+	}
 
 	token := "magic token"