Fixed Micrometer and OpenTelemetry dependency declaration

[ok2c]

@arturobernalg httpclient5-observation module dependency declaration is a mess. I tried my best to correct it but because it know literally nothing about the module and its purpose I need your input.

• What version of Open Telemetry do you intend to use? 1.49.0 or 1.52.0. You declarations were conflicting
• Why was Open Telemetry SDK was marked as runtime? Is it the only backend that the module intents to support or users should be able to choose different backends?
• Why micrometer-core and micrometer-observation were marked optional. They looks very non-optional due to direct imports in the code. What as your intent?

More importantly, do you think the module is ready for GA? Are its APIs ready? Maybe we should skip one minor version and delay a GA release of this module?

[arturobernalg]

@ok2c thanks for cleaning up the POM and for raising these points.

The conflicting OpenTelemetry versions and the SDK as a runtime dependency were just leftovers from some local experiments that I did not clean up properly – my mistake. The intention is to use a single OTEL version (I would suggest 1.52.0, but I am happy to align with whatever you prefer for 5.6) and to depend only on the OTEL API in the module itself, leaving SDK and exporters entirely to the application.

From my side the module is ready to be used and safe to ship as GA: it is purely observational, does not change client behaviour, and lives in an isolated optional module that nothing else depends on, so there is no risk for existing users. If we need to refine the API later, we can still do it via the usual deprecation path without impacting the core or classic/async client APIs.