Update xml/issue4290.xml

Co-authored-by: Jonathan Wakely <[email protected]>

Author: tomaszkam

xml/issue4290.xml

@@ -33,7 +33,7 @@ We propose to correct that oversight and reintroduce the following <i>Mandates</
 Set priority to 2 after reflector poll.
 </p>
 <p>
-The <i>Mandate</i> of <tt>Alignment &gt;= alignof(T)</tt> was put into
+The <i>Mandates</i> of <tt>Alignment &gt;= alignof(T)</tt> was put into
 question, as being too restrictive for general purpose free function.
 </p>
 </discussion>