Bump OpenTelemetry.Exporter.OpenTelemetryProtocol from 1.3.0 to 1.6.0

Bumps [OpenTelemetry.Exporter.OpenTelemetryProtocol](https://github.com/open-telemetry/opentelemetry-dotnet) from 1.3.0 to 1.6.0.
- [Release notes](https://github.com/open-telemetry/opentelemetry-dotnet/releases)
- [Commits](open-telemetry/opentelemetry-dotnet@core-1.3.0...core-1.6.0)

---
updated-dependencies:
- dependency-name: OpenTelemetry.Exporter.OpenTelemetryProtocol
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Directory.Build.targets

@@ -76,7 +76,7 @@
         <!-- open telemetry -->
         <PackageReference Update="OpenTelemetry" Version="1.3.0" />
         <PackageReference Update="OpenTelemetry.Exporter.Console" Version="1.3.0" />
-        <PackageReference Update="OpenTelemetry.Exporter.OpenTelemetryProtocol" Version="1.3.0" />
+        <PackageReference Update="OpenTelemetry.Exporter.OpenTelemetryProtocol" Version="1.6.0" />
         <PackageReference Update="OpenTelemetry.Extensions.Hosting" Version="1.0.0-rc9" />
         <PackageReference Update="OpenTelemetry.Instrumentation.AspNetCore" Version="1.0.0-rc9" />
         <PackageReference Update="OpenTelemetry.Instrumentation.Http" Version="1.0.0-rc9" />