[commands/cache] Avoid use of "(s)" suffix.
[commands/cache] Avoid use of "(s)" suffix.

As @hugovk pointed out, it can cause problems sometimes:

https://github.com/pypa/pip/pull/6391#discussion_r366259867

pradyunsg/pip,sbidoul/pip,sbidoul/pip,pfmoore/pip,pypa/pip,pfmoore/pip,pypa/pip,pradyunsg/pip