Issue #21545: Add .pop example and tweak comment about pure mutation methods.
Patch prepared by David Harrigan.
diff --git a/Misc/ACKS b/Misc/ACKS
index a323006..97d00ea 100644
--- a/Misc/ACKS
+++ b/Misc/ACKS
@@ -507,6 +507,7 @@
 Lynda Hardman
 Derek Harland
 Jason Harper
+David Harrigan
 Brian Harring
 Jonathan Hartley
 Travis B. Hartwell