[dotnet-svcutil.XmlSerializer] set release version label to RTM

Author: imcarolwang

src/svcutilcore/src/dotnet-svcutil.xmlserializer.csproj

@@ -21,7 +21,7 @@
     <MajorVersion>8</MajorVersion>
     <MinorVersion>0</MinorVersion>
     <PatchVersion>0</PatchVersion>
-    <PreReleaseVersionLabel>preview1</PreReleaseVersionLabel>
+    <PreReleaseVersionLabel>rtm</PreReleaseVersionLabel>
     <DisablePackageBaselineValidation>true</DisablePackageBaselineValidation>
     <PackageReleaseNotes>https://github.com/dotnet/wcf/blob/master/release-notes/dotnet-svcutil.xmlserializer-notes.md</PackageReleaseNotes>
     <!-- The partial facade assembly's public key token must exactly match the contract to be filled. -->