Drop active searchable item subscription when changing active item

We were leaking the previous active item's subscription, which meant
that we would receive the `MatchesInvalidated` event as many times as
we changed items.

Co-Authored-By: Thorsten Ball <thorsten@zed.dev>
Co-Authored-By: Mikayla Maki <mikayla@zed.dev>
b151e12890Antonio Scandurra committed on 1/23/2024, 5:31:21 PMparent21e6b09
1 file changedLine totals unavailable