Name the version under development 2.0.0-preview.2 (#856)

The NuGet workflow takes what it publishes from the release tag, so this
property is what a local build and the assembly metadata carry. Left at
preview.1 it would stamp preview.1 into an assembly shipped as preview.2.

AssemblyVersion stays pinned at 2.0.0.0 for the whole of 2.x.

Author: Rafael-SOWNet

Sources/Package.Build.props

@@ -17,7 +17,7 @@
     release tag, so what ships is named by the tag; this is what a local build and the
     assembly metadata carry.
     -->
-    <Version>2.0.0-preview.1</Version>
+    <Version>2.0.0-preview.2</Version>
 
     <!--
     Pinned to the major for the whole of 2.x, and deliberately not tracking Version.