Bump Blazor package versions to preview4

Author: wtgodbe

eng/Versions.props

@@ -13,7 +13,7 @@
     <PreReleaseVersionLabel>preview3</PreReleaseVersionLabel>
     <AssemblyVersion Condition="'$(IsReferenceAssemblyProject)' != 'true'">$(VersionPrefix).0</AssemblyVersion>
     <!-- Blazor WASM packages will not RTM with 3.1 -->
-    <BlazorWASMPreReleaseVersionLabel>preview3</BlazorWASMPreReleaseVersionLabel>
+    <BlazorWASMPreReleaseVersionLabel>preview4</BlazorWASMPreReleaseVersionLabel>
     <!--
       We do not support changing reference assemblies in a patch. This ignores
       the patch version number to ensure assembly version of ref assemblies stays constant