Fix Okta IdP signing cert. (#37078)

[getvictor]

Fixing unreleased Okta IdP signing cert issue which prevented from setting up Okta conditional access.

Testing

• QA'd all new/changed functionality manually

For unreleased bug fixes in a release candidate, one of:

• Confirmed that the fix is not expected to adversely impact load test results

Summary by CodeRabbit

• New Features

• Enhanced the IdP signing certificate download feature with an interactive button that provides real-time loading indicators and improved error handling. Users now receive immediate feedback during the download process with helpful error messages if any issues occur.

• Chores

  • Removed unused import references.

_{✏️ Tip: You can customize this high-level summary in your review settings.}

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(cherry picked from commit 0c2d465)

[codecov]

Codecov Report

❌ Patch coverage is 12.50000% with 14 lines in your changes missing coverage. Please review.
⚠️ Please upload report for BASE (rc-minor-fleet-v4.78.0@32a51df). Learn more about missing BASE report.

Files with missing lines	Patch %	Lines
...ditionalAccessModal/OktaConditionalAccessModal.tsx	14.28%	12 Missing ⚠️
frontend/services/entities/conditional_access.ts	0.00%	2 Missing ⚠️

Additional details and impacted files

@@                    Coverage Diff                    @@
##             rc-minor-fleet-v4.78.0   #37123   +/-   ##
=========================================================
  Coverage                          ?   65.89%           
=========================================================
  Files                             ?     2250           
  Lines                             ?   183863           
  Branches                          ?     7609           
=========================================================
  Hits                              ?   121157           
  Misses                            ?    51644           
  Partials                          ?    11062           

Flag	Coverage Δ
frontend	54.00% <12.50%> (?)

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