fix: Disable unprefixed EME on Safari

@avelad reported that PR #3021 caused a regression.  Rather than
revert the entire thing, we are disabling one part of that change to
make it easier to re-enable once the issue is fixed.  We will also
reopen issue #2999 until this is resolved.

Change-Id: I65d93da903d90668bb19e5248658eb458e8bb5c4

lib/polyfill/patchedmediakeys_apple.js

@@ -15,7 +15,6 @@ goog.require('shaka.util.EventManager');
 goog.require('shaka.util.FakeEvent');
 goog.require('shaka.util.FakeEventTarget');
 goog.require('shaka.util.MediaReadyState');
-goog.require('shaka.util.Platform');
 goog.require('shaka.util.PublicPromise');
 goog.require('shaka.util.StringUtils');
 
@@ -34,6 +33,9 @@ shaka.polyfill.PatchedMediaKeysApple = class {
       return;
     }
 
+    /* Unprefixed EME disabled.  See:
+       https://github.com/google/shaka-player/pull/3021#issuecomment-766999811
+
     // Only tested in Safari 14.
     const safariVersion = shaka.util.Platform.safariVersion();
     if (navigator.requestMediaKeySystemAccess &&
@@ -43,6 +45,7 @@ shaka.polyfill.PatchedMediaKeysApple = class {
       // Unprefixed EME is preferable.
       return;
     }
+    */
 
     shaka.log.info('Using Apple-prefixed EME');