core(audits): remove audio-caption accessibility audit (GoogleChrome#10453)

Author: beaufortfrancois

lighthouse-cli/test/cli/__snapshots__/index-test.js.snap

@@ -195,9 +195,6 @@ Object {
     Object {
       "path": "accessibility/aria-valid-attr",
     },
-    Object {
-      "path": "accessibility/audio-caption",
-    },
     Object {
       "path": "accessibility/button-name",
     },
@@ -490,11 +487,6 @@ Object {
           "id": "aria-valid-attr",
           "weight": 10,
         },
-        Object {
-          "group": "a11y-audio-video",
-          "id": "audio-caption",
-          "weight": 10,
-        },
         Object {
           "group": "a11y-names-labels",
           "id": "button-name",

lighthouse-cli/test/fixtures/a11y/a11y_tester.html

@@ -78,10 +78,6 @@
         aria-checked="0">
       </div>
     </section>
-    <p>audio-caption</p>
-    <section>
-      <audio id="audio-caption"></audio>
-    </section>
     <p>button-name</p>
     <section>
       <button id="button-name"></button>