[css-color-hdr] Remove duplicate productions

Follow-up on 04ccce9.

Author: cdoublev

css-color-hdr-1/Overview.bs

@@ -977,16 +977,14 @@ Mixing Dynamic Range Limits: the ''dynamic-range-limit-mix()'' function {#dynami
 	in a particular, given [=color space=]
 	(rather than the implicit sRGB color space that most of the other color functions operate in).
 
-	In this specification, 
-	the <<colorspace-params>> taken by the ''color()'' function is extended
+	This specification extends the ''color()'' function
 	to allow <a href="#predefined-HDR">predefined color spaces for HDR</a>,
 	in addition to the predefined SDR spaces from [[css-color-4#predefined]]
 	and the relative color syntax from [[css-color-5#relative-colors]].
 
 	Its syntax is now as follows:
 
 	<pre class='prod'>
-		<dfn>&lt;colorspace-params></dfn> = [<<custom-params>> | <<predefined-rgb-params>> | <<xyz-params>>]
 		<dfn>&lt;predefined-rgb></dfn> = srgb | srgb-linear | display-p3 | a98-rgb | prophoto-rgb | rec2020 | 
 			rec2100-pq | rec2100-hlg | rec2100-linear
 	</pre>