fix: fix abstain vote button color

[wa0x6e]

Summary

Closes: #396

Fix ABSTAIN button text not having the correct color.

This was because abstain for highlight vote is index 0, whereas it is 3 for all the other types

How to test

1. Go to http://localhost:8080/#/sep:0x5559e6c038fD0494277ac85ab6576843A6d0187b/proposal/7/votes
2. The ABSTAIN button should now have grey text

[Sekhmet]

We might be actually messing up something with choice values (2 should be abstain, but here it's 0). Taking a look.

[Sekhmet]

Without this PR after highlight change: voting abstain:

voting against:

voting for:

So this PR is not needed, sorry Wan 😆