setup.py: allow msgpack 1.1.1

setup.py

@@ -75,7 +75,7 @@ install_requires = [
     # Please note:
     # using any other msgpack version is not supported by borg development and
     # any feedback related to issues caused by this will be ignored.
-    'msgpack >=0.5.6, <=1.1.0, !=1.0.1',
+    'msgpack >=0.5.6, <=1.1.1, !=1.0.1',
     'packaging',
 ]