Fix phrasing.

wiki/src/doc/about/openpgp_keys/signing_key_revocation.mdwn

@@ -290,7 +290,7 @@ XXX: - Stop before "So, can we count on you for this?"
    the new member.
 
 1. If they agree, ask someone else from the same group to send them
-   their key.
+   their share of the key.
 
    This reveals some membership to other people but it's all-right since
    they have the same share.