Skip flaky test: test_source_lookup_with_proguard

[devinfra-flakiness]

Please help us keep Sentry flake-free by merging this PR while a longer-term
resolution is implemented in issue #93951.

Test: tests/relay_integration/lang/java/test_plugin.py::BasicResolvingIntegrationTest::test_source_lookup_with_proguard

Statistics over the last 30 days:
* Runs Recorded: 641
* Flakes Failed: 0 (0%)
* Flakes Retried: 641 (100%)

Example Flakes:

• https://github.com/getsentry/sentry/actions/runs/15783508731/job/44494684382
• https://github.com/getsentry/sentry/actions/runs/15783035231/job/44493146231
• https://github.com/getsentry/sentry/actions/runs/15782491615/job/44491342051
• https://github.com/getsentry/sentry/actions/runs/15773617919/job/44463102175
• https://github.com/getsentry/sentry/actions/runs/15773600786/job/44463052431

---

See also:
Flaky Test Policy & Responsibilities

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

❌ File not in storage

No result to display due to the CLI not being able to find the file.
Please ensure the file contains junit in the name and automated file search is enabled,
or the desired file specified by the file and search_dir arguments of the CLI.

Additional details and impacted files

@@             Coverage Diff             @@
##           master   #93952       +/-   ##
===========================================
+ Coverage   46.41%   85.58%   +39.17%     
===========================================
  Files       10333    10349       +16     
  Lines      597257   597996      +739     
  Branches    23222    23222               
===========================================
+ Hits       277188   511818   +234630     
+ Misses     319565    85495   -234070     
- Partials      504      683      +179