Bump NUnit from 3.12.0 to 3.13.0

Bumps [NUnit](https://github.com/nunit/nunit) from 3.12.0 to 3.13.0.
- [Release notes](https://github.com/nunit/nunit/releases)
- [Changelog](https://github.com/nunit/nunit/blob/master/CHANGES.md)
- [Commits](nunit/nunit@v3.12...v3.13)

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

Author: dependabot[bot]

src/Directory.Build.props

@@ -34,7 +34,7 @@
         <PackageVersion_MicrosoftTestSdk>16.8.3</PackageVersion_MicrosoftTestSdk>
         <PackageVersion_NSubstitute>4.2.2</PackageVersion_NSubstitute>
         <PackageVersion_CoverletMsBuild>2.9.0</PackageVersion_CoverletMsBuild>
-        <PackageVersion_NUnit>3.12.0</PackageVersion_NUnit>
+        <PackageVersion_NUnit>3.13.0</PackageVersion_NUnit>
         <PackageVersion_GitToolsTesting>1.2.0</PackageVersion_GitToolsTesting>
         <PackageVersion_NUnit3TestAdapter>3.17.0</PackageVersion_NUnit3TestAdapter>
         <PackageVersion_NunitXmlTestLogger>2.1.80</PackageVersion_NunitXmlTestLogger>