doc/go_mem: fix broken paper link in go_mem.html
The link is no longer accessible.
Replace it with the ACM one.
Change-Id: I4095fd07a1bc193568cd93fbf69955ba0ba96f2b
GitHub-Last-Rev:
33b142d6e864d9c59c5fb2bd21dbe4a6fd65ab36
GitHub-Pull-Request: golang/go#70295
Reviewed-on: https://go-review.googlesource.com/c/go/+/626485
Reviewed-by: Cherry Mui <cherryyz@google.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
Auto-Submit: Ian Lance Taylor <iant@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>