Bump Microsoft.NET.Test.Sdk to 18.3.0 (#187)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

tests/Prometheus.Client.MetricPusher.Tests.csproj

@@ -5,7 +5,7 @@
     <IsPackable>false</IsPackable>
   </PropertyGroup>
   <ItemGroup>
-    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="18.0.1" />
+    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="18.3.0" />
     <PackageReference Include="NSubstitute" Version="5.3.0" />
     <PackageReference Include="Testcontainers" Version="4.10.0" />
     <PackageReference Include="coverlet.collector" Version="8.0.0">