Update dependency NSubstitute to v4.4.0

Author: renovate[bot]

Directory.Packages.props

@@ -40,7 +40,7 @@
     <PackageVersion Include="xunit.runner.visualstudio" Version="2.4.4" />
     <PackageVersion Include="xunit" Version="2.4.1" />
     <PackageVersion Include="FluentAssertions" Version="6.6.0" />
-    <PackageVersion Include="NSubstitute" Version="4.3.0" />
+    <PackageVersion Include="NSubstitute" Version="4.4.0" />
     <PackageVersion Include="Serilog.Extensions.Logging" Version="3.1.0" />
     <PackageVersion Include="Serilog.Sinks.Observable" Version="2.0.2" />
     <PackageVersion Include="Serilog.Sinks.XUnit" Version="3.0.3" />