experiment(replays): Use default JSON decoder

[cmanallen]

We're seeing a lot of "The surrogate pair in string is invalid" errors. This root cause seems to be rapidjson. The increase in errors might be attributable to our new canvas changes. Switching to the simplejson default decoder might allow us to parse these JSON messages.

Related to: Tencent/rapidjson#2259

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (059538d) 81.25% compared to head (958f0dd) 81.24%.
Report is 4 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master   #64079      +/-   ##
==========================================
- Coverage   81.25%   81.24%   -0.01%     
==========================================
  Files        5228     5228              
  Lines      230501   230501              
  Branches    45238    45238              
==========================================
- Hits       187288   187275      -13     
- Misses      37365    37373       +8     
- Partials     5848     5853       +5     

Files	Coverage Δ
src/sentry/replays/usecases/ingest/__init__.py	85.00% <100.00%> (ø)

... and 7 files with indirect coverage changes

[sentry-io]

Suspect Issues

This pull request was deployed and Sentry observed the following issues:

• ‼️ RecursionError: maximum recursion depth exceeded while decoding a JSON object from a unicode string sentry.utils.json in loads View Issue

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