Bump Microsoft.NET.Test.Sdk to 18.3.0 (#177)

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

Author: renovate[bot]

tests/Prometheus.Client.AspNetCore.Tests.csproj

@@ -5,7 +5,7 @@
     <NoWarn>$(NoWarn);CS0618</NoWarn>
   </PropertyGroup>
   <ItemGroup>
-    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="18.0.1" />
+    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="18.3.0" />
     <PackageReference Include="xunit.v3" Version="3.2.2 " />
     <PackageReference Include="xunit.runner.visualstudio" Version="3.1.5">
       <PrivateAssets>all</PrivateAssets>