[rfw] Upgrade missed example app (#7545)

`rfw` has multiple example apps - I missed this one in #7521.

Also missed `extension_google_sign_in_as_googleapis_auth` - will need to upgrade that in a follow up PR (it has additional failures after the AGP upgrade, so it isn't a one line fix).

packages/rfw/example/remote/android/build.gradle

@@ -6,7 +6,7 @@ buildscript {
     }
 
     dependencies {
-        classpath 'com.android.tools.build:gradle:7.4.2'
+        classpath 'com.android.tools.build:gradle:8.5.2'
         classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
     }
 }