Update xml/issue4393.xml

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

Author: tomaszkam

xml/issue4393.xml

@@ -24,7 +24,7 @@ Set priority to 2 after reflector poll.
 </p>
 <p>
 This issue is related to lwg <iref ref="4420"/>.
-The constrains needs to be updated to handle conversions between <tt>float</tt>
+The <i>Constrains</i> needs to be updated to handle conversions between <tt>float</tt>
 and <tt>float16_t</tt> and similar cases.  
 </p>
 </discussion>