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)

.github/workflows/rsi-diff.yml

@@ -15,9 +15,12 @@ jobs:
 
       - name: Get changed files
         id: files
-        uses: Ana06/get-changed-files@v1.2
+        uses: Ana06/get-changed-files@v2.3.0
         with:
           format: 'space-delimited'
+          filter: | 
+            **.rsi
+            **.png
 
       - name: Diff changed RSIs
         id: diff