Install System.Text.RegularExpressions to netstandard1.3 and Update Microsoft.AspNetCore.Http.Abstractions

Author: phnx47

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

@@ -27,7 +27,8 @@
   </ItemGroup>
   <ItemGroup Condition=" '$(TargetFramework)' == 'netstandard1.3'">
     <PackageReference Include="System.Net.Http" Version="4.3.4" />
-    <PackageReference Include="Microsoft.AspNetCore.Http.Abstractions" Version="1.1.0" />
+    <PackageReference Include="System.Text.RegularExpressions" Version="4.3.1" />
+    <PackageReference Include="Microsoft.AspNetCore.Http.Abstractions" Version="1.1.2" />
   </ItemGroup>
   <ItemGroup Condition="'$(TargetFramework)' == 'netstandard2.0' OR '$(TargetFramework)' == 'netcoreapp2.2' OR '$(TargetFramework)' == 'netstandard2.1'">
     <PackageReference Include="Microsoft.AspNetCore.Http.Abstractions" Version="2.2.0" />