Unless the browser says an update is available from the "About Google Chrome" section, just ignore. I use to get them all the time for IE and still get those dodgy emails saying that I need to update my bank details. Funy thing is that its normally for Barclays and I dont even bank with them.
So yeah, unless you are sure its genuine, just ignore and try again. Besides, Chrome doesn't have Service Packs like that its trying to make out. They just release an higher version number like most companies and they don't offer antivirus software bundled with it, instead it uses a builtin sandbox to run any scripts in.