Remove Jaeger reporter and sampler customizations

[yurishkuro]

https://github.com/yarpc/yab/pull/233/files#diff-7ddfb3e035b42cd70649cc33393fe32cR381

I recommend removing these two lines and using the default sampler and reporter.

The choice of sampler should have little effect since yab forces sampling via sampling.priority tag anyway, so no reason to have that customization.

The reason for using null reported is a mystery to me, it causes top-level span of the trace not being reported even when they could've been, e.g. when yab is run on a production host. There's no harm in running with the default (remote) reporter here.