[web] Replace ColorPicker with ColorSelector in ThreadSettingsModal

Summary:
We're ready to swap out ColorPicker with ColorSelector.

Leaving ColorPicker in the codebase for now even though it's not being used anywhere... will remove it in a bit.

Depends on D3697

Test Plan:
Looks and works as expected:

Reviewers: def-au1t, palys-swm

Reviewed By: palys-swm

Subscribers: ashoat, Adrian, karol-bisztyga, benschac, yayabosh

Differential Revision: https://phabricator.ashoat.com/D3699