Update ISOWeek.xml (#3820)

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Author: jb817566

xml/System.Globalization/ISOWeek.xml

@@ -49,7 +49,7 @@
       <Docs>
         <param name="date">A date in the Gregorian calendar.</param>
         <summary>Calculates the ISO week number of a given Gregorian date.</summary>
-        <returns>A number between 1 and 53 represnting the ISO week number of the given Gregorian date.</returns>
+        <returns>A number between 1 and 53 representing the ISO week number of the given Gregorian date.</returns>
         <remarks>
           <format type="text/markdown"><![CDATA[