Update helix.proj

Author: wtgodbe

eng/helix/helix.proj

@@ -6,7 +6,7 @@
       This must be reset in order for Build.props to evaluate a list of projects to be tested on Helix.
     -->
     <ProjectToBuild Condition="'$(ProjectToBuild)' == '$(MSBuildProjectFullPath)'"/>
-    <ProjectToBuild Condition="'$(OnlyTestProjectTemplates)' == 'true'">$(RepoRoot)src\ProjectTemplates\**\*.csproj</ProjectToBuild>
+    <ProjectToBuild Condition="'$(OnlyTestProjectTemplates)' == 'true'">$(RepoRoot)src\ProjectTemplates\test\**\*.csproj</ProjectToBuild>
 
     <!--
       Do not load NuGet.targets since this project doesn't reference anything from NuGet. Reduces `msbuild`