Use python -m pip installation method

kianmeng · kianmeng · commit 04778f0efdf9 · 2022-11-24T09:22:04.000+08:00
See https://snarky.ca/why-you-should-use-python-m-pip/
diff --git a/README.rst b/README.rst
@@ -71,7 +71,7 @@ Install
 -------
 Install with pip::
 
-    $ pip install flake8-builtins
+    $ python -m pip install flake8-builtins
 
 Options
 -------
