Remove ArcadeBuildVertical parameter (#18889)

Author: mmitche

src/SourceBuild/content/repo-projects/Directory.Build.props

@@ -82,10 +82,6 @@
     <BuildArgs Condition="'$(SourceBuildUseMonoRuntime)' == 'true'">$(BuildArgs) /p:SourceBuildUseMonoRuntime=$(SourceBuildUseMonoRuntime)</BuildArgs>
   </PropertyGroup>
 
-  <PropertyGroup Condition="'$(DotNetBuildSourceOnly)' != 'true'">
-    <BuildArgs>$(BuildArgs) /p:ArcadeBuildVertical=true</BuildArgs>
-  </PropertyGroup>
-
   <PropertyGroup Condition="'$(DotNetBuildSourceOnly)' == 'true'">
     <BuildArgs>$(BuildArgs) /p:ArcadeBuildFromSource=true</BuildArgs>
     <BuildArgs>$(BuildArgs) /p:DotNetBuildSourceOnly=true</BuildArgs>