chore(similarity): Add seer failure reason to backfill log

[jangjodi]

Add the reason seer post request failed to the similarity seer failure backfill log

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 78.15%. Comparing base (26e6464) to head (e77245b).
Report is 4 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master   #74735   +/-   ##
=======================================
  Coverage   78.14%   78.15%           
=======================================
  Files        6730     6730           
  Lines      300110   300111    +1     
  Branches    51623    51623           
=======================================
+ Hits       234529   234539   +10     
+ Misses      59256    59248    -8     
+ Partials     6325     6324    -1     

Files	Coverage Δ
src/sentry/seer/similarity/grouping_records.py	85.07% <100.00%> (+0.22%)	⬆️
...ping/backfill_seer_grouping_records_for_project.py	91.46% <ø> (ø)

... and 9 files with indirect coverage changes