Rename PeoplePanel to ContactsPanel

Yeah, it's true they're people, but this is a more specific way in which they're people.

Co-Authored-By: Antonio Scandurra <me@as-cii.com>

crates/zed/src/main.rs

@@ -40,7 +40,7 @@ fn main() {
         editor::init(cx, &mut entry_openers);
         go_to_line::init(cx);
         file_finder::init(cx);
-        people_panel::init(cx);
+        contacts_panel::init(cx);
         chat_panel::init(cx);
         project_panel::init(cx);