Remove redundant Exposed=*

The whole interface is Exposed=*, so this doesn't need to be annotated
separately.

Author: ptomato

spec/Overview.html

@@ -808,7 +808,7 @@ <h2>Crypto interface</h2>
 interface Crypto {
   [SecureContext] readonly attribute SubtleCrypto subtle;
   ArrayBufferView getRandomValues(ArrayBufferView array);
-  [Exposed=*, SecureContext] DOMString randomUUID();
+  [SecureContext] DOMString randomUUID();
 };
         </pre>