Resolve "Icons on forks page are to big"

What does this MR do?

Set size for fork icon fix fork button icon color

Are there points in the code the reviewer needs to double check?

should we set a default size for the sprite_icon method? icon.vue currently sets default of 16 - this means forgetting to set a size could mean a slightly-too-large icon rather than a very-obviously-broken one

Screenshots (if relevant)

Before:

After:

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Tests added for this feature/bug
• Review
  • Has been reviewed by UX
  • Has been reviewed by Frontend
• Conform by the merge request performance guides
• Conform by the style guides
• Squashed related commits together
• Internationalization required/considered

What are the relevant issue numbers?

Closes #42046 (closed)