[Test] Update test expectations for #4420 (#4511)

Co-authored-by: github-actions <[email protected]>

Author: webfiltered

browser_tests/fixtures/ComfyPage.ts

@@ -563,6 +563,7 @@ export class ComfyPage {
         if (fileName.endsWith('.webm')) return 'video/webm'
         if (fileName.endsWith('.json')) return 'application/json'
         if (fileName.endsWith('.glb')) return 'model/gltf-binary'
+        if (fileName.endsWith('.avif')) return 'image/avif'
         return 'application/octet-stream'
       }