[main] Remove duplicate PackageReferences (#6586)

[`dotnet 6.0.400`](https://github.com/dotnet/sdk/releases/tag/v6.0.400) is now firing a lint for duplicate `PackageReference` entries.

- `Microsoft.Azure.Devices.Edge.Agent.Diagnostics.Test`: 
    - `StyleCop.Analyzers`

## Azure IoT Edge PR checklist:

edge-agent/test/Microsoft.Azure.Devices.Edge.Agent.Diagnostics.Test/Microsoft.Azure.Devices.Edge.Agent.Diagnostics.Test.csproj

@@ -11,10 +11,6 @@
   <ItemGroup>
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="16.4.0" />
     <PackageReference Include="Moq" Version="4.10.1" />
-    <PackageReference Include="StyleCop.Analyzers" Version="1.1.118">
-      <PrivateAssets>all</PrivateAssets>
-      <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
-    </PackageReference>
     <PackageReference Include="xunit" Version="2.4.1" />
     <PackageReference Include="xunit.runner.visualstudio" Version="2.4.1">
       <PrivateAssets>all</PrivateAssets>

stylecop.props

@@ -5,4 +5,4 @@
       <IncludeAssets>runtime; build; native; contentfiles; analyzers</IncludeAssets>
     </PackageReference>
   </ItemGroup>
-</Project>
+</Project>