Duplicate Proposal for Chromatic GP Noise and GWB Prior Draw

[xiaosong-hu]

The code currently contains duplicate proposal additions for both the Chromatic GP noise prior draw and GWB prior draw, which results in the same proposals being added twice to the sampler cycle.

Chromatic GP noise prior draw is added twice:

1. https://github.com/nanograv/enterprise_extensions/blob/master/enterprise_extensions/hypermodel.py#L281
   
2. https://github.com/nanograv/enterprise_extensions/blob/master/enterprise_extensions/hypermodel.py#L291
   

GWB prior draw is added twice:

1. https://github.com/nanograv/enterprise_extensions/blob/master/enterprise_extensions/hypermodel.py#L301
   
2. https://github.com/nanograv/enterprise_extensions/blob/master/enterprise_extensions/hypermodel.py#L339
   
   This appears to be an unintentional duplication, likely from a copy-paste operation during development. To ensure proper sampling behavior, please remove the duplicate code blocks so that both the Chromatic GP noise prior draw and GWB prior draw are added only once to the sampler cycle.

[jeremy-baier]

This issue should be addressed in #242 — at least the chromatic GP noise prior draws.
The GWB prior draw is not exactly a duplicate because the first one draws from a log-uniform prior for a power-law GWB amplitude regardless of the prior on the amplitude while the later draw just adds prior draws for any signal with the name gw in it, which would include draws from the prior if you have a log-uniform prior on the power-law parameters.