Bump Microsoft.Windows.CsWinRT from 2.1.1 to 2.1.5 (#234)

Bumps [Microsoft.Windows.CsWinRT](https://github.com/microsoft/cswinrt) from 2.1.1 to 2.1.5.
- [Release notes](https://github.com/microsoft/cswinrt/releases)
- [Changelog](https://github.com/microsoft/CsWinRT/blob/master/docs/breakingchanges-rc2.md)
- [Commits](https://github.com/microsoft/cswinrt/commits)

---
updated-dependencies:
- dependency-name: Microsoft.Windows.CsWinRT
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

src/Windows.Internal.Flighting/Windows.Internal.Flighting.csproj

@@ -7,7 +7,7 @@
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="Microsoft.Windows.CsWinRT" Version="2.1.1" />
+    <PackageReference Include="Microsoft.Windows.CsWinRT" Version="2.1.5" />
   </ItemGroup>
 
   <ItemGroup>