refactor: icon to icons for alerts component

[pkdotson]

SUMMARY

This pr changes the removes the old icon component from alert component

BEFORE/AFTER SCREENSHOTS OR ANIMATED GIF

TESTING INSTRUCTIONS

ADDITIONAL INFORMATION

• Has associated issue:
• 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

Merging #15261 (dec0f2f) into master (c7c6375) will decrease coverage by 0.00%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master   #15261      +/-   ##
==========================================
- Coverage   77.25%   77.25%   -0.01%     
==========================================
  Files         971      971              
  Lines       50308    50307       -1     
  Branches     6140     6140              
==========================================
- Hits        38867    38866       -1     
  Misses      11237    11237              
  Partials      204      204              

Flag	Coverage Δ
javascript	71.80% <100.00%> (-0.01%)	⬇️

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Impacted Files	Coverage Δ
superset-frontend/src/components/Alert/index.tsx	100.00% <100.00%> (ø)

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[rusackas]

/testenv up

[github-actions]

@rusackas Ephemeral environment spinning up at http://54.185.25.92:8080. Credentials are admin/admin. Please allow several minutes for bootstrapping and startup.

[github-actions]

Ephemeral environment shutdown and build artifacts deleted.