Update HostApplicationBuilder.xml (dotnet#9128)

* Update HostApplicationBuilder.xml

Fixes dotnet#9111
Incorrect description for `HostApplicationBuilder.Configuration` property

* Apply suggestions from code review

Co-authored-by: Genevieve Warren <[email protected]>

---------

Co-authored-by: Genevieve Warren <[email protected]>

Author: buyaa-n

xml/Microsoft.Extensions.Hosting/HostApplicationBuilder.xml

@@ -143,9 +143,9 @@
         <ReturnType>Microsoft.Extensions.Configuration.ConfigurationManager</ReturnType>
       </ReturnValue>
       <Docs>
-        <summary>Gets a collection of services for the application to compose. This property is useful for adding user-provided or framework-provided services.</summary>
+        <summary>Gets the set of key-value configuration properties.</summary>
         <value>To be added.</value>
-        <remarks>To be added.</remarks>
+        <remarks>The set of properties can be mutated by adding more configuration sources, which will update its current view.</remarks>
       </Docs>
     </Member>
     <Member MemberName="ConfigureContainer&lt;TContainerBuilder&gt;">