Fix typo in HostingAbstractionsHostExtensions.xml

The following sentence:

> Runs an application and block the calling thread...

Should read:

> Runs an application and **blocks** the calling thread...

Author: ericmutta

xml/Microsoft.Extensions.Hosting/HostingAbstractionsHostExtensions.xml

@@ -48,7 +48,7 @@
       </Parameters>
       <Docs>
         <param name="host">The <see cref="T:Microsoft.Extensions.Hosting.IHost" /> to run.</param>
-        <summary>Runs an application and block the calling thread until host shutdown.</summary>
+        <summary>Runs an application and blocks the calling thread until host shutdown.</summary>
         <remarks>To be added.</remarks>
       </Docs>
     </Member>