[css-color-4] Remove fallback from device-cmyk, fix #6721

Author: svgeesus

css-color-4/Overview.bs

@@ -453,8 +453,6 @@ Representing Colors: the <<color>> type</h2>
 	<pre class='prod'>
 	&lt;color> = <<absolute-color-base>> | currentcolor | <<system-color>> | <<device-cmyk()>>
 
-	<dfn>&lt;absolute-color></dfn> = <<absolute-color-base>> | <<absolute-device-cmyk>>
-
 	<dfn>&lt;absolute-color-base></dfn> = <<hex-color>> | <<named-color>> | transparent |
 	    <<rgb()>> | <<rgba()>> | <<hsl()>> | <<hsla()>> | <<hwb()>> |
 	    <<lab()>> | <<lch()>> |
@@ -4442,8 +4440,7 @@ Uncalibrated CMYK Colors: the ''device-cmyk()'' function</h2>
 	The ''device-cmyk()'' function allows authors to specify a color in this way:
 
 	<pre class='prod'>
-		<dfn>device-cmyk()</dfn> = device-cmyk( <<cmyk-component>>{4} [ / <<alpha-value>> ]? , <<color>>? )
-		<dfn>&lt;absolute-device-cmyk></dfn> = device-cmyk( <<cmyk-component>>{4} [ / <<alpha-value>> ]? , <<absolute-color>>? )
+		<dfn>device-cmyk()</dfn> = device-cmyk( <<cmyk-component>>{4} [ / <<alpha-value>> ]? )
 		<dfn>&lt;cmyk-component></dfn> = <<number>> | <<percentage>>
 	</pre>
 
@@ -4458,10 +4455,6 @@ Uncalibrated CMYK Colors: the ''device-cmyk()'' function</h2>
 	It's interpreted identically to the fourth argument of the ''rgb()'' function.
 	If omitted, it defaults to ''100%''.
 
-	The sixth argument specifies the fallback color,
-	used when the user agent doesn't know how to accurately transform the CMYK color to RGB.
-	If omitted, it defaults to the CMYK color <a>naively converted to RGBA</a>.
-
 	Typically, print-based applications will actually store the used colors as CMYK,
 	and send them to the printer in that form.
 	However, such colors do not have a colorimetric interpretation,
@@ -4479,9 +4472,6 @@ Uncalibrated CMYK Colors: the ''device-cmyk()'' function</h2>
 			and the user agent can process ICC profiles,
 			the computed value of the ''device-cmyk()'' function
 			must be the Lab value of the CMYK color.</li>
-		<li>Otherwise, if a valid fallback color has been specified,
-			the computed value of the ''device-cmyk()'' function
-			must be that fallback color.</li>
 		<li>Otherwise,
 			the computed value of the ''device-cmyk()'' function must be
 			the sRGB value of the CMYK color,
@@ -4490,7 +4480,7 @@ Uncalibrated CMYK Colors: the ''device-cmyk()'' function</h2>
 	</ol>
 
 	<div class='example' id="ex-device-cmyk-naive">
-		For example, with no ''@color-profile'' and no fallback specified,
+		For example, with no ''@color-profile'',
 		the following colors are equivalent, using the naive conversion.
 
 		<pre class="lang-css">