Restore trailing blank lines from main

Author: aisk

.github/SECURITY.md

@@ -21,3 +21,4 @@ include and exclude](https://devguide.python.org/security/policy/#what-to-includ
 in vulnerability reports. Following the security policy means the PSRT can
 quickly and efficiently triage your report, not following the security policy
 will only delay triaging your report.
+

Doc/library/asyncio-threading.rst

@@ -151,3 +151,4 @@ and tries again. When the producer is done it calls
 :meth:`~queue.Queue.shutdown`, which causes subsequent
 :meth:`~queue.Queue.get_nowait` calls to raise :exc:`queue.ShutDown`
 so the consumer can exit cleanly.
+

Doc/library/tkinter.colorchooser.rst

@@ -37,3 +37,4 @@ the :class:`~tkinter.commondialog.Dialog` class.
 
    Module :mod:`tkinter.commondialog`
       Tkinter standard dialog module
+