UI: Remove unused @lezer/highlight dependency

[parkhojeong]

@lezer/highlight came in with the CodeMirror-based JSON editor in #43367, became a direct
dependency in #62796, and was left unused after the Monaco migration in #62708.

Validation

• pnpm remove @lezer/highlight
• pnpm install --frozen-lockfile
• pnpm why @lezer/highlight
• pnpm list @lezer/highlight --depth Infinity
• pnpm list @lezer/common --depth Infinity
• pnpm build
• breeze testing ui-e2e-tests

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[choo121600]

Since #68032 is currently discussing whether Monaco Editor should be removed due to ongoing maintenance and stability concerns, I wonder if it would make sense to revisit this change after that discussion reaches a conclusion.

[parkhojeong]

Since #68032 is currently discussing whether Monaco Editor should be removed due to ongoing maintenance and stability concerns, I wonder if it would make sense to revisit this change after that discussion reaches a conclusion.

Thanks for the context. After that discussion, this could be used.