chore: Update line-height in SliceHeaderControl

[geido]

SUMMARY

Removes a hacky usage of font-size and sets the line-height to a fixed value. Line heights will soon be converted to theme variables in a follow-up effort.

BEFORE/AFTER SCREENSHOTS OR ANIMATED GIF

No visual changes

TESTING INSTRUCTIONS

No changes should be observable

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 #19613 (65076e4) into master (4a835a4) will decrease coverage by 0.00%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master   #19613      +/-   ##
==========================================
- Coverage   66.51%   66.50%   -0.01%     
==========================================
  Files        1714     1714              
  Lines       65026    65025       -1     
  Branches     6710     6710              
==========================================
- Hits        43249    43248       -1     
  Misses      20070    20070              
  Partials     1707     1707              

Flag	Coverage Δ
javascript	51.22% <ø> (-0.01%)	⬇️

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

Impacted Files	Coverage Δ
...dashboard/components/SliceHeaderControls/index.tsx	66.25% <ø> (-0.42%)	⬇️

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[michael-s-molina]

Approved with the note that we will come back in a follow-up when the line-height is added to the theme object.