Bump Microsoft.NET.Test.Sdk from 16.3.0 to 16.4.0 (#58)

Bumps [Microsoft.NET.Test.Sdk](https://github.com/microsoft/vstest) from 16.3.0 to 16.4.0.
- [Release notes](https://github.com/microsoft/vstest/releases)
- [Commits](microsoft/vstest@v16.3...v16.4.0)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

src/common.props

@@ -20,7 +20,7 @@
   </PropertyGroup>
   <PropertyGroup>
     <XunitVersion>2.4.1</XunitVersion>
-    <TestSdkVersion>16.3.0</TestSdkVersion>
+    <TestSdkVersion>16.4.0</TestSdkVersion>
     <NetCoreTestVersion>netcoreapp2.1</NetCoreTestVersion>
     <NetStandardVersion>netstandard2.0</NetStandardVersion>
     <NetFrameworkTestVersion>net461</NetFrameworkTestVersion>