i18n(ko): add missing translation for Rendered Map Index

[23tae]

Description

This PR adds the missing Korean translation for the renderedMapIndex filter key in ko/common.json to fix the untranslated TODO: translate placeholder displayed in the UI filter bar.

Screenshots

Before	After

• Checked translation completeness using breeze ui check-translation-completeness --language ko
  

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Was generative AI tooling used to co-author this PR?

• Yes (please specify the tool below)

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Please review this translation.
/cc @choo121600 @onestn @noeunkim

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• Read the Pull Request Guidelines for more information. Note: commit author/co-author name and email in commits become permanently public when merged.
• For fundamental code changes, an Airflow Improvement Proposal (AIP) is needed.
• When adding dependency, check compliance with the ASF 3rd Party License Policy.
• For significant user-facing changes create newsfragment: {pr_number}.significant.rst, in airflow-core/newsfragments. You can add this file in a follow-up commit after the PR is created so you know the PR number.

[choo121600]

Could you attach the output screenshot from breeze ui check-translation-completeness --language ko?

[23tae]

@choo121600 I've updated the PR description to include the requested screenshot. All translations have been verified as complete.

[choo121600]

Nice ,This CI failure seems unrelated to this PR :)
however GitHub Actions is currently experiencing an outage and CI is not running, so I'll check again later before merging 😉