Bump NSubstitute from 4.3.0 to 4.4.0 in /source (#62)

Bumps NSubstitute from 4.3.0 to 4.4.0.

---
updated-dependencies:
- dependency-name: NSubstitute
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

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

Author: dependabot[bot]

source/Tests/Tests.csproj

@@ -11,7 +11,7 @@
       <PackageReference Include="NUnit" Version="3.13.3" />
       <PackageReference Include="Serilog" Version="2.11.0" />
       <PackageReference Include="Serilog.Sinks.TextWriter" Version="2.1.0" />
-      <PackageReference Include="NSubstitute" Version="4.3.0" />
+      <PackageReference Include="NSubstitute" Version="4.4.0" />
       <PackageReference Include="FluentAssertions" Version="6.7.0" />
       <PackageReference Include="NUnit3TestAdapter" Version="4.2.1" />
       <PackageReference Include="TeamCity.VSTest.TestAdapter" Version="1.0.36" />