Editorial: remove “commonly” to reflect actual JSON encoding (w3c#1100)

Co-authored-by: Marcos Cáceres <[email protected]>

index.html

@@ -2647,8 +2647,8 @@ <h2>
         as "high value" (particularly from a privacy perspective).
       </p>
       <p>
-        As the manifest format is JSON and will commonly be encoded using
-        [[UNICODE]], the security considerations described in [[JSON]] and
+        As the manifest format is JSON and will be encoded using [[UNICODE]],
+        the security considerations described in [[JSON]] and
         [[UNICODE-SECURITY]] apply. In addition, because there is no way to
         prevent developers from including custom/unrestrained data in a
         <a>manifest</a>, implementors need to impose their own