vscode-extensions.matklad.rust-analyzer: Add reminder to update script

The release tag was out-of-date even though the extension was updated
regularly. Ideally, the update script might increment it on its own,
like the rust-analyzer update script already does.

pkgs/applications/editors/vscode/extensions/rust-analyzer/update.sh

@@ -47,3 +47,5 @@ else
 
     ./"$node_packages"/generate.sh
 fi
+
+echo "Remember to also update the revisionTag and hash in default.nix!"