Remove generated pipelines and update gocd-jsonnet

[mattgauntseo-sentry]

GoCD is now setup to read the pipelines directly from jsonnet, so there is no need to keep the generated pipelines in this repo.

This PR also does the following:

• Update the gocd-jsonnet libs (new feature that allows removing a region from pipedream in case of an incident)
• Remove the original/old symbolicator pipeline

#skip-changelog

[codecov]

Codecov Report

Merging #1290 (e6749e0) into master (147e0e6) will decrease coverage by 0.01%.
The diff coverage is n/a.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1290      +/-   ##
==========================================
- Coverage   76.79%   76.78%   -0.01%     
==========================================
  Files          87       87              
  Lines       14295    14295              
==========================================
- Hits        10978    10977       -1     
- Misses       3317     3318       +1     

[mattgauntseo-sentry]

I'll merge this after hackweek