Update Directory.Build.prop for 3.9.2 release

Change-Id: Ia22bc0e8ed67bf8323721366b347461857f23fb8
Reviewed-on: https://review.couchbase.org/c/couchbase-net-client/+/244395
Reviewed-by: Jeffry Morris <jeffrymorris@gmail.com>
Tested-by: Build Bot <build@couchbase.com>

Author: davidkelly

Directory.Build.props

@@ -20,7 +20,7 @@
   </PropertyGroup>
   <PropertyGroup>
     <!-- update this after a release-->
-    <CouchbaseNetClientReleasedVersion>3.9.1</CouchbaseNetClientReleasedVersion>
+    <CouchbaseNetClientReleasedVersion>3.9.2</CouchbaseNetClientReleasedVersion>
   </PropertyGroup>
   <PropertyGroup>
     <!-- libraries typically include NetStandardTargets for widest use cases -->