Bump OpenTelemetry.Instrumentation.AspNetCore from 1.7.1 to 1.8.1

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>

tour-of-heroes-api.csproj

@@ -21,7 +21,7 @@
     <PackageReference Include="OpenTelemetry.Extensions.Hosting" Version="1.7.0" />
 
     <!-- Instrumentation -->
-    <PackageReference Include="OpenTelemetry.Instrumentation.AspNetCore" Version="1.7.1" />
+    <PackageReference Include="OpenTelemetry.Instrumentation.AspNetCore" Version="1.8.1" />
     <PackageReference Include="OpenTelemetry.Instrumentation.EntityFrameworkCore" Version="1.0.0-beta.10" />
     <PackageReference Include="OpenTelemetry.Instrumentation.Http" Version="1.8.0" />    
     <PackageReference Include="OpenTelemetry.Instrumentation.Process" Version="0.5.0-beta.4" />