Further tweaking on gpg signing key notice

CHANGES.md

@@ -7,9 +7,12 @@ This release removes the deprecated `GET /_synapse/admin/v1/users/<user_id>` adm
 
 This release requires Application Services to use type `m.login.application_service` when registering users via the `/_matrix/client/r0/register` endpoint to comply with the spec. Please ensure your Application Services are up to date.
 
-If you are using the `packages.matrix.org` Debian repository for Synapse packages, note that our gpg signing keys have rotated and the old pair have expired. You can pull the latest keys with:
+If you are using the `packages.matrix.org` Debian repository for Synapse packages, 
+note that we have recently updated the expiry date on the gpg signing key. If you see an 
+error similar to `The following signatures were invalid: EXPKEYSIG F473DD4473365DE1`, you
+will need to get a fresh copy of the keys. You can do so with:
 
-```
+```sh
 sudo wget -O /usr/share/keyrings/matrix-org-archive-keyring.gpg https://packages.matrix.org/debian/matrix-org-archive-keyring.gpg
 ```