fix teams dep on botbuilder-core (#1871)

pip refuses to install deps that are not hosted on pypi. oops. But botbuilder loosened their deps so that shouldnot be a problem any more with botbuilder-core 4.13+

setup.cfg

@@ -94,15 +94,9 @@ connector_slack =
 connector_webex =
 	webexteamssdk>=1.6
 connector_teams =
-	# these wheels are modified copies of the wheels from the wheels PyPI
-	# to loosen overly aggressive dependency pinning so they don't conflict
-	# with our other deps.
-	# We should be able to drop these once this is resolved upstream:
-	# https://github.com/microsoft/botbuilder-python/issues/1467
-	botbuilder_core@https://github.com/opsdroid/wheels-for-teams-connector/releases/download/4.11.0/botbuilder_core-4.11.0-py3-none-any.whl
-	botframework_connector@https://github.com/opsdroid/wheels-for-teams-connector/releases/download/4.11.0/botframework_connector-4.11.0-py2.py3-none-any.whl
-	# what we really care about:
-	botbuilder-core>=4.11.0
+	# Before 4.13, botbuilder aggressively pinned dependencies so that they conflicted with our other deps.
+	# see: https://github.com/microsoft/botbuilder-python/issues/1467
+	botbuilder-core>=4.13.0
 connector_telegram =
   emoji>=0.6.0
 # parsers