Removes references to ~please_ack in other protocols

[swcurran]

~please_ack was recently retired. This PR removes the remaining references to ~please_ack in other protocols. Most relevant to the community is the removal from the issue-credential and present-proof protocols -- which need to be update in AIP 2.0 to include recent clarifications (including this one).

This is not controversial as we have already decided to retire ~please_ack -- this is just post retirement cleanup.

I think this PR could just be merged with approvals from a @TelegramSam, @TimoGlastra, @genaris but could also wait for an Aries Working Group meeting.

[swcurran]

Updated the RFCs to have change log entries for the change. Made the change logs consistently formatted across the updated RFCs.