build(deps): update opentelemetry-sdk requirement from ~> 1.5.0 to ~> 1.6.0

Updates the requirements on [opentelemetry-sdk](https://github.com/open-telemetry/opentelemetry-ruby) to permit the latest version.

Updates `opentelemetry-sdk` to 1.6.0
- [Release notes](https://github.com/open-telemetry/opentelemetry-ruby/releases)
- [Changelog](https://github.com/open-telemetry/opentelemetry-ruby/blob/main/sdk/CHANGELOG.md)
- [Commits](open-telemetry/opentelemetry-ruby@opentelemetry-sdk/v1.5.0...opentelemetry-sdk/v1.6.0)

---
updated-dependencies:
- dependency-name: opentelemetry-sdk
  dependency-type: direct:production
  dependency-group: opentelemetry-deps-ruby
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

ruby/src/otel/layer/Gemfile

@@ -1,5 +1,5 @@
 source 'https://rubygems.org'
 
-gem 'opentelemetry-sdk', '~> 1.5.0'
+gem 'opentelemetry-sdk', '~> 1.6.0'
 gem 'opentelemetry-exporter-otlp', '~> 0.29.0'
 gem 'opentelemetry-instrumentation-aws_lambda', '~> 0.1.0'