Documentation: add semicolons to iframe example allow option (#2400)

docs/widgets/services/iframe.md

@@ -27,7 +27,7 @@ widget:
   src: http://example.com
   classes: h-60 sm:h-60 md:h-60 lg:h-60 xl:h-60 2xl:h-72 # optional, use tailwind height classes, see https://tailwindcss.com/docs/height
   referrerPolicy: same-origin # optional, no default
-  allowPolicy: autoplay fullscreen gamepad # optional, no default
+  allowPolicy: autoplay; fullscreen; gamepad # optional, no default
   allowFullscreen: false # optional, default: true
   loadingStrategy: eager # optional, default: eager
   allowScrolling: no # optional, default: yes