docs: fix simple typo, rsponse -> response

[timgates42]

There is a small typo in docs/docs_env/Lib/site-packages/pip-1.0-py2.5.egg/pip/download.py.

Should read response rather than rsponse.

Semi-automated pull request generated by https://github.com/timgates42/meticulous/blob/master/docs/NOTE.md