drafts: Fix draft controls being offscreen on mobile web.
drafts: Fix draft controls being offscreen on mobile web.

This was caused by an interaction with the controls being positioned
absolutely -103px from the right edge of the element, which is clearly
a hack.

Replace that with a simple `float: right` construction, with the top
padding aligned.

Fixes #22512.

zulip/zulip,rht/zulip,zulip/zulip,andersk/zulip,zulip/zulip,zulip/zulip,rht/zulip,andersk/zulip,rht/zulip,andersk/zulip,zulip/zulip,zulip/zulip,rht/zulip,rht/zulip,rht/zulip,zulip/zulip,andersk/zulip,andersk/zulip,rht/zulip,andersk/zulip,andersk/zulip