Update dependency

Author: phnx47

src/Prometheus.Client.AspNetCore/Prometheus.Client.AspNetCore.csproj

@@ -23,7 +23,7 @@
     <None Include="../../icon.png" Pack="true" Visible="false" PackagePath="" />
   </ItemGroup>
   <ItemGroup>
-    <PackageReference Include="Prometheus.Client" Version="3.1.0" />
+    <PackageReference Include="Prometheus.Client" Version="[3.1.0,4.0.0)" />
   </ItemGroup>
   <ItemGroup Condition=" '$(TargetFramework)' == 'netstandard1.3'">
     <PackageReference Include="System.Net.Http" Version="4.3.4" />