update nuspec dependency

Author: Tim Bussmann

packaging/nuget/nservicebus.testing.nuspec

@@ -19,7 +19,7 @@
       <frameworkAssembly assemblyName="System.Core" targetFramework="net452" />
     </frameworkAssemblies>
     <dependencies>
-      <dependency id="NServiceBus" version="[6.0.0-rc0001, 7.0.0)" />
+      <dependency id="NServiceBus" version="[6.0.0, 7.0.0)" />
     </dependencies>
   </metadata>
   <files>