docs(css): Remove Firefox select element default

Request Type: docs

How to reproduce: View the docs from Firefox. The version picker's select elements arrow is still showing.

Component(s): 

Impact: small

Complexity: small

This issue is related to: 

**Detailed Description:**



**Other Comments:**

In firefox the version picker's dropdown from the default select element is still showing. This is a hack to force FF to hide the ugly default.