fix(web): draw one divider where the actions menu has one group

[nkyryliuk]

Fixes a doubled divider in the pull request actions menu on feat/pull-requests-page.

The problem

The menu's action group — the draft toggle and the merge strategies — opens with a divider whether or not it holds anything, and the merge strategies draw a second divider above themselves whether or not the draft toggle is there to be separated from.

Two reachable cases:

A host with no draft of its own. Bitbucket declares actions: ["merge", "close"], so the draft toggle never renders. Nothing lands between the divider that opens the group and the one the merge strategies draw, and the two sit together.

A draft whose "Ready for review" is already the header button. The toggle is withheld so the action is not offered twice, and the strategies are hidden because a draft cannot be merged — so the group is empty and the dividers that open and close it sit together.

Before / after

Captured on this branch, before and after the fix, in one browser session. The server was pointed at a local Bitbucket API double serving a synthetic repository and pull request, so the app exercises its real Bitbucket path end to end. The doubled hairline sits above Merge; counted from the DOM, role="separator" inside the open menu goes from 4 to 3 with the menu items unchanged.

Before	After

The change

The two members of the group are named once, and every divider around it is drawn from the same answer as its contents:

• the group's own divider stays where it is, since the items below it are always there
• the merge strategies draw a divider only when the draft toggle is above them
• the divider closing the group is drawn only when the group has something in it

One file, no behaviour change beyond the dividers. apps/web typechecks with no new errors and the tests under src/components/pullRequest pass.