[css-fonts-4] update UTR51 ref to UTS51

Author: svgeesus

css-fonts-4/Overview.bs

@@ -1880,17 +1880,17 @@ The <dfn id="at-font-face-rule">''@font-face''</dfn> rule</h3>
     The 'variations' requirement refers to the support of font variations,
     commonly implemented in [[!OPENTYPE]] with the
     <code>avar</code>, <code>cvar</code>, <code>fvar</code>, <code>gvar</code>, <code>HVAR</code>, <code>MVAR</code>, <code>STAT</code>, and <code>VVAR</code> tables,
-    as well as in [[!AAT]] using the <code>avar</code>, <code>cvar</code>, <code>fvar</code>, and <code>gvar</code> tables.
+    as well as in [[!AAT-FEATURES]] using the <code>avar</code>, <code>cvar</code>, <code>fvar</code>, and <code>gvar</code> tables.
     The section on [[#basic-font-props]] as well as the section on [[#font-variation-props]]
     describe properties that interact with these facilities.
 
     The 'color' requirement lists various types of color font file technologies.
     Each of the arguments to the 'color' function represents a table
-    inside [[!OPENTYPE]] or [[!AAT]] fonts which must be supported
+    inside [[!OPENTYPE]] or [[!AAT-FEATURES]] fonts which must be supported
     to satisfy this requirement.
 
     The 'palettes' requirement refers to support for font palettes,
-    commonly implemented in the [[!OPENTYPE]] and [[!AAT]]
+    commonly implemented in the [[!OPENTYPE]] and [[!AAT-FEATURES]]
     with the <code>CPAL</code> table.
     The section on [[#color-font-support]] describes properties that interact with these facilities.
 
@@ -4757,7 +4757,7 @@ considered when the user-agent decides whether to use emoji presentation or text
 
 	<dt><dfn>unicode</dfn></dt>
 	<dd>
-		Code points are rendered in accordance with [[!UTR51]]
+		Code points are rendered in accordance with [[!UTS51]]
 		as either emoji-default, text-default, or text-only,
 		depending on the values of the Emoji and Emoji_Presentation
 		properties for each