update for 6.0 GA branding (#5135)

Author: HongGit

eng/Versions.props

@@ -8,7 +8,7 @@
     <WcfAssemblyVersion>6.0.0.0</WcfAssemblyVersion>
     <!-- To produce shipping versions in non-official builds, instead of default fixed dummy version number (42.42.42.42). -->
     <DotNetUseShippingVersions>true</DotNetUseShippingVersions>
-    <PreReleaseVersionLabel>rc</PreReleaseVersionLabel>
+    <PreReleaseVersionLabel>rtm</PreReleaseVersionLabel>
     <PreReleaseVersionIteration>
     </PreReleaseVersionIteration>
     <!-- Use the compiler in the CLI instead of in the sdk, since the sdk one doesn't work with netcoreapp3.0 yet -->