GitHub UI integration setting should not repeat "optional"

When !57389 (merged) is merged, the GitHub project integration settings will have (optional) repeated:

I think it would be better if only the upper (optional) remained, and we should remove it from the checkbox text.

However, as explained by @tomquirk in the linked thread:

I would recommend that we address this in a follow-up - we'll need to add this capability to dynamic_field.vue.

For now, is there a reason we can't merge the current change? It looks good to me, but we can reach out to UX for an additional opinion if you like (@lvanc would be the best person).

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The following discussion from !57389 (merged) should be addressed:

• @msedlakjakubowski started a discussion: (+8 comments)

  Note for the reviewers:

  I've added `(optional) here and now it shows both in the section's name and the checkbox.

  

  It's not pretty, but I think it's better than not having it there at all.