[Python] .python-version should NOT be ignored (github#3274)

Python.gitignore

@@ -82,7 +82,9 @@ profile_default/
 ipython_config.py
 
 # pyenv
-.python-version
+#   For a library or package, you might want to ignore these files since the code is
+#   intended to run in multiple environments; otherwise, check them in:
+# .python-version
 
 # pipenv
 #   According to pypa/pipenv#598, it is recommended to include Pipfile.lock in version control.