chore: Update font-sizes in ReportModal

[geido]

SUMMARY

This PR removes hacky usages of font-sizes by replacing them with the exact font-sizes available in the theme config.

BEFORE

AFTER

TESTING INSTRUCTIONS

1. Open the Report Modal from a Dashboard
2. Make sure the font-sizes look balanced

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

Merging #19593 (1ca0e91) into master (761d5c4) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master   #19593   +/-   ##
=======================================
  Coverage   66.68%   66.68%           
=======================================
  Files        1681     1681           
  Lines       64316    64320    +4     
  Branches     6565     6565           
=======================================
+ Hits        42888    42894    +6     
  Misses      19733    19733           
+ Partials     1695     1693    -2     

Flag	Coverage Δ
javascript	51.52% <100.00%> (+0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
...set-frontend/src/components/ReportModal/styles.tsx	87.50% <100.00%> (ø)
...c/views/CRUD/data/database/DatabaseModal/index.tsx	32.79% <0.00%> (ø)
...ntend/packages/superset-ui-core/src/color/utils.ts	100.00% <0.00%> (+2.85%)	⬆️
...shboard/util/charts/getFormDataWithExtraFilters.ts	77.77% <0.00%> (+5.55%)	⬆️
...frontend/src/profile/components/CreatedContent.tsx	77.77% <0.00%> (+6.34%)	⬆️

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[michael-s-molina]

LGTM