+= instead of <<

[Vagab]

comment

Description

Describe your changes:
this pr creates a copy instead of mutating the original, which fixes the issue and my company's test suite

[Vagab]

@sl0thentr0py I'm not sure who to tag for a review but wanted to get some eyes on this since it's blocking our upgrade to sentry 1.17

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 97.09%. Comparing base (7b00b25) to head (d628506).

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2317      +/-   ##
==========================================
- Coverage   98.66%   97.09%   -1.57%     
==========================================
  Files         205      175      -30     
  Lines       13422    11756    -1666     
==========================================
- Hits        13243    11415    -1828     
- Misses        179      341     +162     

Components	Coverage Δ
sentry-ruby	99.03% <100.00%> (ø)
sentry-rails	45.70% <ø> (-51.73%)	⬇️
sentry-sidekiq	96.98% <ø> (ø)
sentry-resque	96.76% <ø> (ø)
sentry-delayed_job	98.91% <ø> (ø)
sentry-opentelemetry	100.00% <ø> (ø)

Files	Coverage Δ
sentry-ruby/lib/sentry/test_helper.rb	100.00% <100.00%> (ø)

... and 43 files with indirect coverage changes