fix(capitalization): Capitalizing the 'metric' label in Pivot Tables

[rusackas]

SUMMARY

Capitalizing the 'metric' header according to capitalization guidelines.

BEFORE/AFTER SCREENSHOTS OR ANIMATED GIF

Before:

After:

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

Merging #24265 (e01a63f) into master (f6e769a) will not change coverage.
The diff coverage is 0.00%.

❗ Current head e01a63f differs from pull request most recent head ae00092. Consider uploading reports for the commit ae00092 to get more accurate results

@@           Coverage Diff           @@
##           master   #24265   +/-   ##
=======================================
  Coverage   68.31%   68.31%           
=======================================
  Files        1957     1957           
  Lines       75597    75597           
  Branches     8222     8222           
=======================================
  Hits        51641    51641           
  Misses      21848    21848           
  Partials     2108     2108           

Flag	Coverage Δ
javascript	54.72% <0.00%> (ø)

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Impacted Files	Coverage Δ
...s/plugin-chart-pivot-table/src/PivotTableChart.tsx	0.00% <0.00%> (ø)

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