Corrected a typo. (#5099)

Corrected a typo in EnvironmentName property description.

Author: tanveerbadar

xml/Microsoft.Extensions.Hosting/IHostEnvironment.xml

@@ -105,8 +105,7 @@
         <ReturnType>System.String</ReturnType>
       </ReturnValue>
       <Docs>
-        <summary>Gets or sets the name of the environment. The host automatically sets this property to the value of the
-            of the "environment" key as specified in configuration.</summary>
+        <summary>Gets or sets the name of the environment. The host automatically sets this property to the value of the "environment" key as specified in configuration.</summary>
         <value>To be added.</value>
         <remarks>To be added.</remarks>
       </Docs>