Bump Microsoft.NET.Test.Sdk from 18.8.1 to 18.9.0 (#99)

Author: dependabot[bot]

MimeTypes.Tests/MimeTypes.Tests.csproj

@@ -13,7 +13,7 @@
     <ItemGroup>
         <PackageReference Include="NUnit" Version="4.6.1" />
         <PackageReference Include="NUnit3TestAdapter" Version="6.2.0" />
-        <PackageReference Include="Microsoft.NET.Test.Sdk" Version="18.8.1" />
+        <PackageReference Include="Microsoft.NET.Test.Sdk" Version="18.9.0" />
     </ItemGroup>
 
     <ItemGroup>