BIP-372: Moving Andrew Poelstra from author to ACK section

Basing on bitcoin#1293 (comment)

Author: dr-orlovsky

README.mediawiki

@@ -1068,7 +1068,7 @@ Those proposing changes should consider that ultimately consent may rest with th
 | [[bip-0372.mediawiki|372]]
 | Applications
 | Pay-to-contract tweak fields for PSBT
-| Maxim Orlovsky, Andrew Poelstra
+| Maxim Orlovsky
 | Standard
 | Draft
 |-

bip-0372.mediawiki

@@ -3,7 +3,6 @@
   Layer: Applications
   Title: Pay-to-contract tweak fields for PSBT
   Author: Maxim Orlovsky <[email protected]>
-          Andrew Poelstra <[email protected]>
   Discussions-To: <[email protected]>
   Comments-URI: https://github.com/bitcoin/bips/wiki/Comments:BIP-0372
   Status: Draft
@@ -161,7 +160,9 @@ WIP
 
 ==Acknowledgements==
 
-TBD
+Author is grateful to Andrew Poelstra, who provided an initial set of ideas
+and information on his previous work on the topic basing on which this standard
+was designed.
 
 
 ==Test vectors==