chore(deps): update dependency prometheus.client to v6

Author: renovate[bot]

src/Prometheus.Client.HttpRequestDurations.csproj

@@ -6,7 +6,7 @@
   </PropertyGroup>
   <ItemGroup>
     <FrameworkReference Include="Microsoft.AspNetCore.App" />
-    <PackageReference Include="Prometheus.Client" Version="5.2.0" />
+    <PackageReference Include="Prometheus.Client" Version="6.0.0" />
   </ItemGroup>
   <ItemGroup>
     <InternalsVisibleTo Include="$(MSBuildProjectName).Tests, PublicKey=002400000480000094000000060200000024000052534131000400000100010043c098de06c8d023082f50046903a938a6357a83ac284dc6caaa4522d1dd4febe72ff9287e2db59bee71183be94be70cc8199e80c38c6bf970037839748071b1628c76fe975e803d31f6f59ff710d4a83bb78783d69ae06db640234a01b7b78707e185c8a8b50641e42335d309f82a311ae8b48d957a6c563e23c1f76108008d" />