Fix any type usage in proprietary/ (#5949)

# Description of Changes
Follow on from #5934, expanding `any` type usage ban to the
`proprietary/` folder

frontend/eslint.config.mjs

@@ -83,7 +83,10 @@ export default defineConfig(
   },
   // Folders that have been cleaned up and are now conformant - stricter rules enforced here
   {
-    files: ['src/saas/**/*.{js,mjs,jsx,ts,tsx}'],
+    files: [
+      'src/proprietary/**/*.{js,mjs,jsx,ts,tsx}',
+      'src/saas/**/*.{js,mjs,jsx,ts,tsx}',
+    ],
     languageOptions: {
       parserOptions: {
         project: true,