Editorial: Add missing comma after "json"

Author: jamierocks

fetch.bs

@@ -2202,7 +2202,7 @@ bookkeeping details by the <a for=/>fetch</a> algorithm.
 
 <p>A <dfn export>subresource request</dfn> is a <a for=/>request</a>
 whose <a for=request>destination</a> is "<code>audio</code>", "<code>audioworklet</code>",
-"<code>font</code>", "<code>image</code>", "<code>json</code>" "<code>manifest</code>",
+"<code>font</code>", "<code>image</code>", "<code>json</code>", "<code>manifest</code>",
 "<code>paintworklet</code>", "<code>script</code>", "<code>style</code>", "<code>track</code>",
 "<code>video</code>", "<code>xslt</code>", or the empty string.