[css-borders-4][editorial] Remove range of k parameter from superellipse() (#12460)

Author: cdoublev

css-borders-4/Overview.bs

@@ -1250,7 +1250,7 @@ Corner Shaping: the 'corner-*-shape' properties</h3>
 	<pre class=prod>
 		<dfn><<corner-shape-value>></dfn> = <l>''corner-shape/round''</l> | <l>''corner-shape/scoop''</l> | <l>''corner-shape/bevel''</l> | <l>''corner-shape/notch''</l> | <l>''corner-shape/square''</l> | <l>''corner-shape/squircle''</l> |
 		                       <<superellipse()>>
-		<dfn>superellipse()</dfn> = superellipse(<<number [-&infin;,&infin;]>> | infinity | -infinity)
+		<dfn>superellipse()</dfn> = superellipse(<<number>> | infinity | -infinity)
 	</pre>
 
 	<dl dfn-type="value" dfn-for="<corner-shape-value>, corner-shape">