[css-values-5] Editorial: fix scope of random() values (#11920)

According to the definitions data model, `dfn-for` needs to a contain a
"comma-separated list" of definitions. The spec used `|` to separate values
for `random()` and `<random-value-sharing>`.

Author: tidoust

css-values-5/Overview.bs

@@ -2089,7 +2089,7 @@ Generating a Random Numeric Value: the ''random()'' function</h3>
 		in the styles across several elements,
 		via the ''random()/match-element'' value (or its absence)
 
-	<dl dfn-type=value dfn-for="random()|<random-value-sharing>">
+	<dl dfn-type=value dfn-for="random(),<random-value-sharing>">
 		: <dfn>auto</dfn>
 		::	Each [=random function=] in an element's styles
 			will use a distinct [=random base value=].