springboot Remove dependency management for Wavefront SDK

Note that the version number is a bit unusual here as 2.3 is a maintenance release of the 2.xline.

Comment From: snicoll

We've decided to rather remove dependency management for the Wavefront SDK and let the 3rd party starter take care of the version. Spring Boot itself doesn't do much with the API besides customizing a WavefrontSender via configuration.

The 3rd party starter, however, does auto-configure much more of the infrastructure (e.g. tracing) so it makes sense that it is in control of the version of the SDK.