fix: add imports back to celery file

[sadpandajoe]

SUMMARY

Fixes issue #29708. When we were adding ruff in #28158, I'm guessing it was removed as these were unused imports.

BEFORE/AFTER SCREENSHOTS OR ANIMATED GIF

TESTING INSTRUCTIONS

ADDITIONAL INFORMATION

• Has associated issue:
• Required feature flags:
• Changes UI
• Includes DB Migration (follow approval process in SIP-59)
  • Migration is atomic, supports rollback & is backwards-compatible
  • Confirm DB migration upgrade and downgrade tested
  • Runtime estimates and downtime expectations provided
• Introduces new feature or API
• Removes existing feature or API

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 1 line in your changes missing coverage. Please review.

Project coverage is 83.69%. Comparing base (76d897e) to head (5ab7fb2).
Report is 581 commits behind head on master.

Files	Patch %	Lines
superset/tasks/celery_app.py	0.00%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           master   #29921       +/-   ##
===========================================
+ Coverage   60.48%   83.69%   +23.21%     
===========================================
  Files        1931      527     -1404     
  Lines       76236    38053    -38183     
  Branches     8568        0     -8568     
===========================================
- Hits        46114    31850    -14264     
+ Misses      28017     6203    -21814     
+ Partials     2105        0     -2105     

Flag	Coverage Δ
hive	49.02% <0.00%> (-0.15%)	⬇️
javascript	?
mysql	76.78% <0.00%> (?)
postgres	76.85% <0.00%> (?)
presto	53.56% <0.00%> (-0.24%)	⬇️
python	83.69% <0.00%> (+20.21%)	⬆️
sqlite	76.34% <0.00%> (?)
unit	60.36% <0.00%> (+2.73%)	⬆️

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[villebro]

LGTM - I restarted the flaky MySQL IT which had failed