[css-2018] Bikeshed reference fix

Author: frivoal

css-2018/Overview.bs

@@ -535,7 +535,7 @@ Proprietary and Non-standardized Features</h4>
 
 	To avoid clashes with future CSS features,
 	the CSS2.1 specification reserves a
-	<dfn lt="vendor prefix | vendor-prefixed | prefixed | unprefixed"><a href="https://www.w3.org/TR/CSS21/syndata.html#vendor-keywords">prefixed syntax</a></dfn> [[!CSS2]]
+	<dfn lt="vendor prefix | vendor-prefixed | prefixed | unprefixed"><a href="https://www.w3.org/TR/CSS2/syndata.html#vendor-keywords">prefixed syntax</a></dfn> [[!CSS2]]
 	for proprietary and experimental extensions to CSS.
 	A CSS feature is a <dfn>proprietary extension</dfn> if it is meant for use
 	in a closed environment accessible only to a single vendor's user agent(s).
@@ -707,7 +707,7 @@ Safe to Release pre-CR Exceptions</h2>
 <h3 id="terms">Terms Index</h3>
 
 <index type="dfn" status="TR" spec="
-	css21,
+	css2,
 	css-syntax-3,
 	css-style-attr-1,
 	mediaqueries-3,
@@ -749,7 +749,7 @@ Safe to Release pre-CR Exceptions</h2>
 <h3 id="selectors">Selector Index</h3>
 
 <index type="selector" status="TR" spec="
-	css21,
+	css2,
 	css-syntax-3,
 	css-style-attr-1,
 	mediaqueries-3,
@@ -792,7 +792,7 @@ Safe to Release pre-CR Exceptions</h2>
 At-Rule Index</h3>
 
 <index type="at-rule" status="TR" spec="
-	css21,
+	css2,
 	css-syntax-3,
 	css-style-attr-1,
 	mediaqueries-3,
@@ -834,7 +834,7 @@ At-Rule Index</h3>
 <h3 id="properties">Property Index</h3>
 
 <index type="property" status="TR" spec="
-	css21,
+	css2,
 	css-syntax-3,
 	css-style-attr-1,
 	mediaqueries-3,
@@ -876,7 +876,7 @@ At-Rule Index</h3>
 <h3 id="values">Values Index</h3>
 
 <index type="value" status="TR" spec="
-	css21,
+	css2,
 	css-syntax-3,
 	css-style-attr-1,
 	mediaqueries-3,