update prometheus.client to 6.0.0

Author: phnx47

src/Prometheus.Client.AspNetCore.csproj

@@ -7,7 +7,7 @@
   </PropertyGroup>
   <ItemGroup>
     <FrameworkReference Include="Microsoft.AspNetCore.App" />
-    <PackageReference Include="Prometheus.Client" Version="[5.2.0,6.0.0)" />
+    <PackageReference Include="Prometheus.Client" Version="6.0.0" />
   </ItemGroup>
   <ItemGroup>
     <InternalsVisibleTo Include="$(MSBuildProjectName).Tests, PublicKey=00240000048000009400000006020000002400005253413100040000010001008be6f2b28dd255318050634aca9465e8d012e309e1d8165462810ca599355ecc0ec05f67fd8d0dac9dabe6df4636764262c742574fa17eb243862c3349521ecff57153ecd557059560a73b0c5ef3cf1587a763c30acdb9222decb309a9425e29b1ed402398d1312e87947e73e03282d2a66156d6ad2bbf7cf924e349a0e9d59d" />