fixup! feat: add agoric-upgrade-18 (proposal 83)

update README

proposals/83:upgrade-18/README.md

@@ -1,9 +1,5 @@
 # Proposal to upgrade the chain software
 
-This holds the draft proposal for agoric-upgrade-18, which will be added to
-[agoric-3-proposals](https://github.com/Agoric/agoric-3-proposals) after it
-passes.
-
-The "binaries" property of `upgradeInfo` is now required since Cosmos SDK 0.46,
-however it cannot be computed for an unreleased upgrade. To disable the check,
-`releaseNotes` is set to `false`.
+This reflects agoric-upgrade-18, which was adopted on mainnet by [governance
+proposal 83](https://ping.pub/agoric/gov/83) at block height 17842500 and
+block time 2025-01-10T11:11:56.366090454Z.