Bump MSTest.TestAdapter (#1247)

Bumps [MSTest.TestAdapter](https://github.com/microsoft/testfx) from 1.3.2 to 1.4.0.
- [Release notes](https://github.com/microsoft/testfx/releases)
- [Commits](microsoft/testfx@v1.3.2...1.4.0)

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

Author: dependabot-preview[bot]

core/getting-started/unit-testing-using-mstest/PrimeService.Tests/PrimeService.Tests.csproj

@@ -6,7 +6,7 @@
 
   <ItemGroup>
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="15.9.0" />
-    <PackageReference Include="MSTest.TestAdapter" Version="1.3.2" />
+    <PackageReference Include="MSTest.TestAdapter" Version="1.4.0" />
     <PackageReference Include="MSTest.TestFramework" Version="1.4.0" />
   </ItemGroup>