Add matrix-org-archive-keyring package as Recommends

This is so installations will pull in the keyring package, allowing us
to update the expiry time of the `packages.matrix.org` repository.

debian/control

@@ -37,6 +37,7 @@ Depends:
 # so we put perl:Depends in Suggests rather than Depends.
 Recommends:
  ${shlibs1:Recommends},
+ matrix-org-archive-keyring,
 Suggests:
  sqlite3,
  ${perl:Depends},