Fix issue where note persisted after note publication

There is no changelog entry needed because drafts are still an
unreleased feature.

Changelog-None
Signed-off-by: Daniel D’Aquino <daniel@daquino.me>
Closes: https://github.com/damus-io/damus/issues/2836

damus/Views/PostView.swift

@@ -230,6 +230,7 @@ struct PostView: View {
                 damus_state.drafts.post = nil
         }
 
+        damus_state.drafts.save(damus_state: damus_state)
     }
     
     func load_draft() -> Bool {