fix(plugins/plugin-carbon-themes): missing import of medium font weight

[starpit]

Fixes #4320

Description of what you did:

My PR is a:

• 💥 Breaking change
• 🐛 Bug fix
• 💅 Enhancement
• 🚀 New feature

Please confirm that your PR fulfills these requirements

• Multiple commits are squashed into one commit.
• The commit message follows Conventional Commits, which allows us to autogenerate release notes; e.g. fix(plugins/plugin-k8s): fixed annoying bugs
• All npm dependencies are pinned.

[codecov]

Codecov Report

Merging #4321 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #4321   +/-   ##
=======================================
  Coverage   59.37%   59.37%           
=======================================
  Files          74       74           
  Lines        2400     2400           
  Branches      583      583           
=======================================
  Hits         1425     1425           
  Misses        748      748           
  Partials      227      227           

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