title: Getting `Parameter Types cannot be optional` when using optional params in my step definition
body: <ol>
  <li>I upgraded to cucumber gem 4.0.0.rc.1</li>
  <li>When I run a scenario that has steps with optional parameter, cucumber complains <code>Parameter types cannot be optional:</code></li>
  </ol>
  
  <p>Example:
  step definition:
  <code>Given I have a ({string} ) cucumber</code></p>
  
  <p>feature steps:</p>
  
  <pre><code>Given I have a 'blue' cucumber
  Given I have a cucumber
  </code></pre>
  
  <ol>
  <li>Looks like a fix was merged in for this issue: <a href="https://github.com/cucumber/cucumber/pull/561" rel="nofollow noreferrer">https://github.com/cucumber/cucumber/pull/561</a></li>
  <li>But, I am still seeing the error I described above.</li>
  <li>I tried:
  <code>Given I have a \\({string} ) cucumber</code> 
  <code>Given I have a \({string} ) cucumber</code></li>
  </ol>