ci: make perf tests only alert on failure

[NicholasBlaskey]

Description

Fix alerts always happening instead of just happening on failure.

Test Plan

After this lands see if I get pinged.

Commentary (optional)

Checklist

• Changes have been manually QA'd
• User-facing API changes need the "User-facing API Change" label.
• Release notes should be added as a separate file under docs/release-notes/.
  See Release Note for details.
• Licenses should be included for new code which was copied and/or modified from any external code.

Ticket

[netlify]

✅ Deploy Preview for determined-ui canceled.

Name	Link
🔨 Latest commit	329dc69
🔍 Latest deploy log	https://app.netlify.com/sites/determined-ui/deploys/65bcf130bb6cc500080325cd

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (ef656bc) 47.72% compared to head (329dc69) 47.72%.
Report is 4 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #8790      +/-   ##
==========================================
- Coverage   47.72%   47.72%   -0.01%     
==========================================
  Files        1049     1049              
  Lines      167250   167250              
  Branches     2241     2241              
==========================================
- Hits        79814    79813       -1     
- Misses      87278    87279       +1     
  Partials      158      158              

Flag	Coverage Δ
backend	43.22% <ø> (-0.01%)	⬇️
harness	64.32% <ø> (ø)
web	42.54% <ø> (ø)

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see 1 file with indirect coverage changes