update branding to preview4 (#50049)

eng/Versions.props

@@ -7,7 +7,7 @@
     <MinorVersion>0</MinorVersion>
     <PatchVersion>0</PatchVersion>
     <PreReleaseVersionLabel>preview</PreReleaseVersionLabel>
-    <PreReleaseVersionIteration>3</PreReleaseVersionIteration>
+    <PreReleaseVersionIteration>4</PreReleaseVersionIteration>
     <!-- Set assembly version to align with major and minor version,
          as for the patches and revisions should be manually updated per assembly if it is serviced. -->
     <AssemblyVersion>$(MajorVersion).$(MinorVersion).0.0</AssemblyVersion>