🚑 Hotfix the dependency on more-itertools

`more-itertools` has a bug in their package metadata. They
have dropped the testing of Python 3.5 from their CI but
forgot to state this in the distribution package metadata.
This is why we need these conditionals to work around the
problem.

Refs:
* more-itertools/more-itertools#578
* more-itertools/more-itertools#579

setup.cfg

@@ -63,7 +63,15 @@ install_requires =
   backports.functools_lru_cache; python_version < '3.3'
   selectors2; python_version< '3.4'
   six>=1.11.0
-  more_itertools>=2.6
+  # NOTE: `more-itertools` has a bug in their package metadata. They
+  # NOTE: have dropped the testing of Python 3.5 from their CI but
+  # NOTE: forgot to state this in the distribution package metadata.
+  # NOTE: This is why we need these conditionals below.
+  # Refs:
+  # * https://github.com/more-itertools/more-itertools/issues/578
+  # * https://github.com/more-itertools/more-itertools/pull/579
+  more_itertools >= 2.6, < 8.11.0; python_version < '3.6'
+  more_itertools >= 2.6; python_version >= '3.6'
   jaraco.functools
 
 [options.extras_require]