Stop generating docs in samples and tests

Removes generation of documentation files for samples and tests. This is
a vestige from using the older Stylecop tool in this repo, which needs
the doc files to inspect.

The deleterious effect of this is getting warnings about missing
documentation on samples, and forcing contributors and maintainers to
write nonsense comments to workaround the warning.

Also removed references to stylecop, since we no longer use it.

samples/Directory.Build.props

@@ -5,8 +5,6 @@
     <!-- Set Output Path for samples-->
     <OutputPath>$(RepoRoot)bin\$(Configuration)\samples\$(MSBuildProjectName)\</OutputPath>
 
-    <!-- Stylecop needs the documentation file to exist -->
-    <DocumentationFile>$(OutputPath)$(MSBuildProjectName).xml</DocumentationFile>
     <IsPackable>false</IsPackable>
   </PropertyGroup>
 </Project>

src/Directory.Build.props

@@ -5,7 +5,6 @@
   <PropertyGroup>
     <OutputPath>$(RepoRoot)bin\$(Configuration)\prod\$(MSBuildProjectName)\</OutputPath>
 
-    <!-- Stylecop needs the documentation file to exist -->
     <DocumentationFile>$(OutputPath)$(MSBuildProjectName).xml</DocumentationFile>
   </PropertyGroup>
 

test/Directory.Build.props

@@ -5,10 +5,6 @@
     <!-- Set Output Path for tests-->
     <OutputPath>$(RepoRoot)bin\$(Configuration)\test\$(MSBuildProjectName)\</OutputPath>
 
-    <!-- Stylecop needs the documentation file to exist -->
-    <DocumentationFile>$(OutputPath)$(MSBuildProjectName).xml</DocumentationFile>
     <IsPackable>false</IsPackable>
-    <NoWarn>$(NoWarn),1573,1591,1712</NoWarn>
-    <StylecopSuppressionsFile>$(StylecopSuppressionsFile);$(MSBuildThisFileDirectory)..\properties\stylecop\TestStylecopSuppressions.cs</StylecopSuppressionsFile>
   </PropertyGroup>
 </Project>