Update or remove public-keys snip

[floehopper]

This snip currently contains public SSH keys for Chris R & James M.

We should decide whether we want to keep this page. If we do we should add a key for Chris L and ensure the other two are up-to-date. If we don't we should remove it.

If we decide to keep it, we should probably improve the look of the page, perhaps by rendering it as plain text without a layout - currently it doesn't loo great!

Note that I recently renamed it (and thus its URL path) from public_keys.snip to public-keys.snip without adding a redirect.