Bump System.CommandLine from 2.0.5 to 2.0.6 (#344)

---
updated-dependencies:
- dependency-name: System.CommandLine
  dependency-version: 2.0.6
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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Author: dependabot[bot]

Directory.Packages.props

@@ -17,7 +17,7 @@
     <PackageVersion Include="Microsoft.Windows.CsWin32" Version="0.3.275" />
     <PackageVersion Include="MSTest.TestAdapter" Version="4.1.0" />
     <PackageVersion Include="MSTest.TestFramework" Version="4.2.1" />
-    <PackageVersion Include="System.CommandLine" Version="2.0.5" />
+    <PackageVersion Include="System.CommandLine" Version="2.0.6" />
     <PackageVersion Include="System.Drawing.Common" Version="10.0.5" />
     <PackageVersion Include="xunit" Version="2.6.2" />
     <PackageVersion Include="xunit.runner.visualstudio" Version="2.5.4" />