Update Environment.xml (#3793)

Author: birken25

xml/System/Environment.xml

@@ -2267,8 +2267,8 @@ The following example creates environment variables for the <xref:System.Environ
         <ReturnType>System.String</ReturnType>
       </ReturnValue>
       <Docs>
-        <summary>Gets the user name of the person who is currently logged on to the operating system.</summary>
-        <value>The user name of the person who is logged on to the operating system.</value>
+        <summary>Gets the user name of the person who is associated with the current thread.</summary>
+        <value>The user name of the person who is associated with the current thread.</value>
         <remarks>
           <format type="text/markdown"><![CDATA[