build(deps): Bump ReactiveMarbles.SourceGenerator.TestNuGetHelper (#210)

Bumps [ReactiveMarbles.SourceGenerator.TestNuGetHelper](https://github.com/reactivemarbles/SourceGenerator.TestNuGetHelper) from 1.2.1 to 1.2.21.
- [Release notes](https://github.com/reactivemarbles/SourceGenerator.TestNuGetHelper/releases)
- [Commits](reactivemarbles/SourceGenerator.TestNuGetHelper@1.2.1...1.2.21)

---
updated-dependencies:
- dependency-name: ReactiveMarbles.SourceGenerator.TestNuGetHelper
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

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

src/ReactiveMarbles.PropertyChanged.SourceGenerator.Builders/ReactiveMarbles.PropertyChanged.SourceGenerator.Builders.csproj

@@ -13,7 +13,7 @@
 
   <ItemGroup>
     <PackageReference Include="Microsoft.CodeAnalysis.CSharp" Version="3.11.0" PrivateAssets="all" />
-    <PackageReference Include="ReactiveMarbles.SourceGenerator.TestNuGetHelper" Version="1.2.1" />
+    <PackageReference Include="ReactiveMarbles.SourceGenerator.TestNuGetHelper" Version="1.2.21" />
   </ItemGroup>
 
 </Project>