Update new label form

What does this MR do and why?

• Unify label form between group/project/admin
  • Remove unnecessary hr
• Reorganize and remove some preset colors
  • Why? Not sure why we'd need this many suggestions when we have the color picker. Also it looks nice when it's organized like a 🌈

Screenshots or screen recordings

Before	After

How to set up and validate locally

• Go to New label page in project/group/admin

#398228 (closed)