Omit a warning when attempting to use cucumber-expressions in regular expressions

Example of this:

```js
Given(/^foo {string}/, () => {});
```

This is unequivocally an error and we can give a more appropriate message than that "a step definition is missing". Furthermore, users that really need this can supress the error like

```js
Given(/^foo {string}/, { supressCucumberExpressionWarning: true }, () => {});
```