Update MP4RA URL

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=207278934

library/core/src/main/java/com/google/android/exoplayer2/util/MimeTypes.java

@@ -252,7 +252,7 @@ public final class MimeTypes {
 
   /**
    * Derives a mimeType from MP4 object type identifier, as defined in RFC 6381 and
-   * http://www.mp4ra.org/object.html.
+   * https://mp4ra.org/#/object_types.
    *
    * @param objectType The objectType identifier to derive.
    * @return The mimeType, or null if it could not be derived.