fix(registry): remove invalid media from caption components (#2454)

* fix(registry): remove invalid media from caption components

* test(registry): enforce nested media contracts

registry/components/caption-parallax-layers/demo.html

@@ -36,15 +36,6 @@
         background: #000;
       }
 
-      #bg-video {
-        position: absolute;
-        inset: 0;
-        z-index: 1;
-        width: 100%;
-        height: 100%;
-        object-fit: cover;
-      }
-
       /* Behind captions: big red 3D text */
       .behind-caption-layer {
         position: absolute;
@@ -154,17 +145,6 @@
       data-width="1920"
       data-height="1080"
     >
-      <video
-        id="bg-video"
-        muted
-        playsinline
-        preload="auto"
-        data-start="0"
-        data-duration="8"
-        data-track-index="0"
-        data-has-audio="false"
-      ></video>
-
       <div class="behind-caption-layer" aria-hidden="true">
         <div id="behind-stage" class="behind-safe-zone"></div>
       </div>