Change style of unit label on UnitControl to the standard label color when UnitControl only has a single unit type

[iamthomasbishop]

A recent PR on the web side fixed an issue with the native-mobile UnitControl component. The fix necessarily disables interactions with the unit part of the control, but the text label still maintains its active link/button style.

To avoid potential confusion, let's change the label color of the unit part of UnitControl to the standard cell label color—specifically in cases where UnitControl only has a single unit type.

To Reproduce
Steps to reproduce the behavior:

1. Add Columns block
2. Select an individual Column
3. Open block settings by tapping on ⚙️ icon
4. Note that the Width setting has a unit control with the active link/button style

[hypest]

@AmandaRiu will try to get through this one as part of groundskeeping. cc @mchowning

[AmandaRiu]

@AmandaRiu will try to get through this one as part of groundskeeping. cc @mchowning

I had spoken to Matt C. last week about this and said if I didn't get to it during groundskeeping, I'd would during this week - so I'll be working on it this week 👍