bpo-36503: remove references to 'aix3' and 'aix4' (GH-12658)

diff --git a/Misc/ACKS b/Misc/ACKS
index df6be59..19c7e43 100644
--- a/Misc/ACKS
+++ b/Misc/ACKS
@@ -476,6 +476,7 @@
 Mark Favas
 Sergey Fedoseev
 Boris Feld
+M. Felt
 Thomas Fenzl
 Niels Ferguson
 Francisco Fernández Castaño