[css-values-4] Ensure all uses of 'case-insensitive' link to the Infra definition.

Author: tabatkins

css-values-4/Overview.bs

@@ -1558,7 +1558,7 @@ Absolute Lengths: the ''cm'', ''mm'', ''Q'', ''in'', ''pt'', ''pc'', ''px'' unit
 	(This change was made because too much existing content relies on the assumption of 96dpi,
 	and breaking that assumption broke the content.)
 
-	Note: Values are case-insensitive and serialize as lower case, for example 1Q serializes as 1q.
+	Note: Units are [=ASCII case-insensitive=] and serialize as lower case, for example 1Q serializes as 1q.
 
 	The <dfn export>reference pixel</dfn> is the visual angle of one pixel on a device with a pixel density of 96dpi
 	and a distance from the reader of an arm's length.
@@ -1730,7 +1730,7 @@ Frequency Units: the <<frequency>> type and ''Hz'', ''kHz'' units</h3>
 	All <<frequency>> units are <a>compatible</a>,
 	and ''hz'' is their <a>canonical unit</a>.
 
-	Note: Values are case-insensitive and serialize as lower case, for example 1Hz serializes as 1hz.
+	Note: Units are [=ASCII case-insensitive=] and serialize as lower case, for example 1Hz serializes as 1hz.
 
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