Upgrade rsi-diff's changed files action | Make it only return rsi and png changes...

Upgrade rsi-diff's changed files action | Make it only return rsi and png changes (#29185)

It was brought up to me in https://github.com/space-wizards/space-station-14/pull/29179#issuecomment-2177140740 (and from a dm from them) that space bars can cause issues with the rsi bot.

Upon investigation its case we use "space-delimited" on the "get changes files" check. Which returns ALL changed files. Even if the change has nothing to do with png's or rsi's (example a downstream merging upstream)