Migrate tests from "model/preference_test.go" to use testify (#12640)

* Update preference_test

* Update preference_test.go to use require package

* remove nil check for json decoder

model/preference_test.go

@@ -57,9 +57,7 @@ func TestPreferencePreUpdate(t *testing.T) {
 	preference.PreUpdate()
 
 	var props map[string]string
-	if err := json.NewDecoder(strings.NewReader(preference.Value)).Decode(&props); err != nil {
-		t.Fatal(err)
-	}
+	require.Nil(t, json.NewDecoder(strings.NewReader(preference.Value)).Decode(&props))
 
 	require.Equal(t, "#ff0000", props["color"], "shouldn't have changed valid props")
 	require.Equal(t, "#faf", props["color2"], "shouldn't have changed valid props")