api!: remove dc_all_work_done()

Also cleaned up test_connectivity()
which tested that state does not flicker to WORKING
when there are no messages to be fetched.
The state is expected to flicker to WORKING
when checking for new messages,
so the tests were outdated since
change 3b0b2379b8

python/src/deltachat/events.py

@@ -158,12 +158,6 @@ class FFIEventTracker:
 
             self.get_matching("DC_EVENT_CONNECTIVITY_CHANGED")
 
-    def wait_for_all_work_done(self):
-        while True:
-            if self.account.all_work_done():
-                return
-            self.get_matching("DC_EVENT_CONNECTIVITY_CHANGED")
-
     def ensure_event_not_queued(self, event_name_regex):
         __tracebackhide__ = True
         rex = re.compile(f"(?:{event_name_regex}).*")