Remove account collapse bug workaround

Unable to reproduce the bug where collapsing an account with lots of
rooms corrupts the ListView, did updating to Qt 5.14.2 do something?

With the workaround removed, the 0.2s delay when removing batch of
ListView items (e.g. when filtering) is gone.

src/backend/models/model.py

@@ -1,7 +1,6 @@
 # SPDX-License-Identifier: LGPL-3.0-or-later
 
 import itertools
-import time
 from bisect import bisect
 from contextlib import contextmanager
 from threading import RLock
@@ -194,22 +193,13 @@ class Model(MutableMapping):
                 yield None
             finally:
                 indice = self._active_batch_remove_indice
-                groups = [list(group) for item, group in itertools.groupby(indice)]
-                last   = None
-
-                if groups:
-                    last = groups[-1].pop()
-                    if not groups[-1]:
-                        del groups[-1]
+                groups = [
+                    list(group) for item, group in itertools.groupby(indice)
+                ]
 
                 for grp in groups:
-                    ModelItemDeleted(self.sync_id, index=grp[0], count=len(grp))
-
-                # Seems QML ListView has an horrible bug where removing a large
-                # amount of items at once will result in a corrupted empty display,
-                # this dumb workaround is the only way I've found
-                if last:
-                    time.sleep(0.2)
-                    ModelItemDeleted(self.sync_id, index=last, count=1)
+                    ModelItemDeleted(
+                        self.sync_id, index=grp[0], count=len(grp),
+                    )
 
                 self._active_batch_remove_indice = None