Bump Microsoft.NET.Test.Sdk from 18.3.0 to 18.4.0 (#376)

---
updated-dependencies:
- dependency-name: Microsoft.NET.Test.Sdk
  dependency-version: 18.4.0
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

src/Directory.Packages.props

@@ -13,7 +13,7 @@
     <PackageVersion Include="Microsoft.EntityFrameworkCore.SqlServer" Version="10.0.5" />
     <PackageVersion Include="Npgsql" Version="10.0.2" />
     <PackageVersion Include="Npgsql.EntityFrameworkCore.PostgreSQL" Version="10.0.1" />
-    <PackageVersion Include="Microsoft.NET.Test.Sdk" Version="18.3.0" />
+    <PackageVersion Include="Microsoft.NET.Test.Sdk" Version="18.4.0" />
     <PackageVersion Include="NUnit" Version="4.5.1" />
     <PackageVersion Include="NUnit3TestAdapter" Version="6.2.0" />
     <PackageVersion Include="coverlet.collector" Version="8.0.1" />