[css-values-4] Remove outdated issue, and slightly reword note for clarity.

Author: tabatkins

css-values-4/Overview.bs

@@ -1259,10 +1259,12 @@ Ratios: the <<ratio>> type</h3>
 	unless both numbers are zero,
 	in which case the computed value is the pair (1, 0) (same as ''1 / 0'').
 
-	Note: This makes the behavior of ''calc(0 / 0)'' and ''0 / 0'' consistent,
-	which is generally true in all other cases.
-
-	Issue: This is being discussed in <a href="https://github.com/w3c/csswg-drafts/issues/4954">Issue 4954</a>.
+	Note: This makes the behavior of ''calc(0 / 0)''
+	(an ordinary division,
+	which resolves to ''NaN''
+	and is then "censored" to ''infinity'')
+	consistent with the ratio ''0 / 0'';
+	this consistency is generally true in all other cases.
 
 	If two <<ratio>>s need to be compared,
 	divide the first number by the second,