Nit: Add explicit python dependency on colorama

[oskirby]

Description

We have had a string of dependabot PR's that fail to build on Windows and after some digging it seems that the problem is due to a Windows-only dependency on the colorama package. We don't explicitly use this anywhere, but it gets pulled in via Glean (glean-parser -> click -> colorama).

However, dependabot doesn't seem to process platform-specific dependencies so this gets completely ignored and is automatically stripped out everytime it tries to update requirements.txt. To fix this, let's just add an explicit dependency on colorama.

Checklist

• My code follows the style guidelines for this project
• I have not added any packages that contain high risk or unknown licenses (GPL, LGPL, MPL, etc. consult with DevOps if in question)
• I have performed a self review of my own code
• I have commented my code PARTICULARLY in hard to understand areas
• I have added thorough tests where needed