My Google Chrome.app is too big. Can I remove previous versions from the Content folder?

It should, afaik, only keep the 2 last versions.

You can safely delete any older than the latest two - then keep an eye on it to make sure it doesn't happen again.

It's likely a glitch that has prevented it keeping up to date. It would be worth checking if it has all versions back to 31.0 or whether there is a time-gap, then just the last two.
If there is a gap, then there's the possibility that the glitch has cleared, but didn't auto-clean up versions from earlier.

An .app package, btw, is simply a folder - nothing more complex than that. Add .app to any folder & watch it change.
The size reported ought to change next time it's accessed, though at worst could take a reboot.