Remove pep8ify as a "current" Python formatter (#1114)

https://pypi.org/project/pep8ify/ has not been updated in 9 years and is therefor not a current Python formatted.

Perhaps https://pypi.org/project/black/ could be mentioned in its place.
diff --git a/yapf/__init__.py b/yapf/__init__.py
index dd0feff..a0406e2 100644
--- a/yapf/__init__.py
+++ b/yapf/__init__.py
@@ -19,7 +19,7 @@
 that line. It then uses a priority queue to figure out what the best formatting
 is --- i.e., the formatting with the least penalty.
 
-It differs from tools like autopep8 and pep8ify in that it doesn't just look for
+It differs from tools like autopep8 in that it doesn't just look for
 violations of the style guide, but looks at the module as a whole, making
 formatting decisions based on what's the best format for each line.