Bump OpenTelemetry.Instrumentation.AspNetCore in /e2e/dotnet

Bumps [OpenTelemetry.Instrumentation.AspNetCore](https://github.com/open-telemetry/opentelemetry-dotnet) from 1.7.1 to 1.8.1.
- [Release notes](https://github.com/open-telemetry/opentelemetry-dotnet/releases)
- [Commits](open-telemetry/opentelemetry-dotnet@Instrumentation.Http-1.7.1...Instrumentation.Http-1.8.1)

---
updated-dependencies:
- dependency-name: OpenTelemetry.Instrumentation.AspNetCore
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>

e2e/dotnet/dotnet.csproj

@@ -11,7 +11,7 @@
         <PackageReference Include="OpenTelemetry.Exporter.Console" Version="1.8.0" />
         <PackageReference Include="OpenTelemetry.Exporter.OpenTelemetryProtocol" Version="1.8.0" />
         <PackageReference Include="OpenTelemetry.Extensions.Hosting" Version="1.8.0" />
-        <PackageReference Include="OpenTelemetry.Instrumentation.AspNetCore" Version="1.7.1" />
+        <PackageReference Include="OpenTelemetry.Instrumentation.AspNetCore" Version="1.8.1" />
         <PackageReference Include="Serilog.Enrichers.Environment" Version="2.3.0" />
         <PackageReference Include="Serilog.Sinks.Async" Version="1.5.0" />
         <PackageReference Include="Serilog.Sinks.OpenTelemetry" Version="1.2.0" />