[ietf-dkim] Change to Section 6

[John Levine]

>>6. Verifier Actions
>>
>>  Since a signer MAY remove or revoke a public key at any time, it is
>>  recommended that verification occur in a timely manner. In many
>>  configurations, the most timely place is during acceptance by the
>>  border MTA or shortly thereafter. [In particular, deferring
>>  verification until the message is accessed by the end user is
>>  discouraged.]
>>
>>This precaution should be removed!!
>
>I disagree with Doug and agree with the wording in the current document.

I'm with Paul, I do not want to reopen the arguments about how long a
verification key should or shouldn't be around.

R's,
John