`StateLabel` should have the `issueClosed` colour updated

[anleac]

Describe the bug
Component at hand: https://primer.style/react/StateLabel

Closed issues on GitHub have a new colour for the background of their state label, which is no longer red.

New:

State label still shows:

Create a StateLabel component with the state being issueClosed, you will witness a state with a red background.

Expected behavior
The background colour should be set to: rgb(137, 87, 229) - I believe this is the same as the merged colour used currently for the state pullMerged

Screenshots
Attached above.

Desktop (please complete the following information):
All browsers.