Update repository descriptions for both TraitsUI and Pyface

The GitHub repository description (the text in the "About" section of the GitHub webpage) for TraitsUI reads:

> TraitsUI: Traits-capable windowing framework

The description for Pyface reads:

> pyface: traits-capable windowing framework

These descriptions are fairly prominent on the main Enthought GitHub page:

For resolving confusion about the difference between TraitsUI and Pyface, could we come up with better descriptions?

Note that the descriptions are specified in Terraform, so while we can update descriptions directly, we'd need to push them through IT to make the changes stick..