fix(seer grouping): Stop checking for missing groups when handling processed results

[lobsterkatie]

When Seer sends back information on similar groups, there's no guarantee that those groups still exist on the Sentry side. Therefore, in the similar issues endpoint, we surround our code which handles the Seer results with a try-except, in case we look for a group which isn't there. Now that the Seer data is first being processed by the SeerSimilarIssueData.from_raw factory method, though, we no longer have to worry about missing groups, because from_raw will error out and not create a SeerSimilarIssueData instance if the group doesn't exist.

This therefore removes the try-except, which then allows us to use a simple list comprehension to build the return value of the endpoint's get_formatted_results helper.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 80.00%. Comparing base (6c80b1e) to head (082b775).

Additional details and impacted files

@@            Coverage Diff             @@
##           master   #70670      +/-   ##
==========================================
- Coverage   80.01%   80.00%   -0.01%     
==========================================
  Files        6507     6507              
  Lines      290842   290836       -6     
  Branches    50126    50126              
==========================================
- Hits       232706   232693      -13     
- Misses      57700    57707       +7     
  Partials      436      436              

Files	Coverage Δ
...y/api/endpoints/group_similar_issues_embeddings.py	100.00% <100.00%> (+1.92%)	⬆️

... and 5 files with indirect coverage changes