remove preview from buildConfig.xml (#2310)

Author: jennyf19

buildConfiguration.xml

@@ -3,7 +3,7 @@
   <nugetVersion>3.5.0-rc-1285</nugetVersion>
   <runtimes>net461,netstandard2.0</runtimes>
   <assemblyVersion>7.0.0</assemblyVersion>
-  <nugetSuffix>preview</nugetSuffix>
+  <nugetSuffix></nugetSuffix>
   <projects>
     <src>
       <project name="Microsoft.IdentityModel.Logging" />