fix(demo-mode): make _sync_project_artifact_bundle failsafe

[constantinius]

Related to: https://linear.app/getsentry/issue/TET-622/symbols-not-appearing-on-sandbox-environment

[sentry-io]

🔍 Existing Issues For Review

Your pull request is modifying functions with the following pre-existing issues:

📄 File: src/sentry/demo_mode/tasks.py

Function	Unhandled Issue
_sync_project_artifact_bundle	ProjectArtifactBundle.DoesNotExist: ProjectArtifactBundle matching query does not exist. sen... Event Count: 5

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[codecov]

Codecov Report

Attention: Patch coverage is 66.66667% with 1 line in your changes missing coverage. Please review.

✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
src/sentry/demo_mode/tasks.py	66.66%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           master   #93376       +/-   ##
===========================================
+ Coverage   41.27%   80.76%   +39.49%     
===========================================
  Files       10259    10286       +27     
  Lines      592078   593033      +955     
  Branches    23028    23028               
===========================================
+ Hits       244401   478986   +234585     
+ Misses     347245   113615   -233630     
  Partials      432      432