Bump MSTest.TestAdapter from 2.1.2 to 2.2.1

Bumps [MSTest.TestAdapter](https://github.com/microsoft/testfx) from 2.1.2 to 2.2.1.
- [Release notes](https://github.com/microsoft/testfx/releases)
- [Commits](microsoft/testfx@v2.1.2...v2.2.1)

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

tests/AJBasicUnitTests/packages.config

@@ -1,5 +1,5 @@
 <?xml version="1.0" encoding="utf-8"?>
 <packages>
-  <package id="MSTest.TestAdapter" version="2.1.2" targetFramework="net472" />
+  <package id="MSTest.TestAdapter" version="2.2.1" targetFramework="net472" />
   <package id="MSTest.TestFramework" version="2.2.1" targetFramework="net472" />
 </packages>