text: reduce lang. specific mecab-ko

[Borda]

What does this PR do?

Reduce language specific, if need rather refer in docs

Before submitting

• Was this discussed/agreed via a Github issue? (no need for typos and docs improvements)
• Did you read the contributor guideline, Pull Request section?
• Did you make sure to update the docs?
• Did you write any new necessary tests?

PR review

Anyone in the community is free to review the PR once the tests have passed.
If we didn't discuss your PR in Github issues there's a high chance it will not be merged.

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Make sure you had fun coding 🙃

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📚 Documentation preview 📚: https://torchmetrics--2456.org.readthedocs.build/en/2456/

[codecov]

Codecov Report

Merging #2456 (dfc21e0) into master (d03ca5e) will decrease coverage by 29%.
The diff coverage is n/a.

Additional details and impacted files

@@           Coverage Diff            @@
##           master   #2456     +/-   ##
========================================
- Coverage      69%     40%    -29%     
========================================
  Files         307     307             
  Lines       17421   17421             
========================================
- Hits        11995    6946   -5049     
- Misses       5426   10475   +5049     

[Borda]

Well, this is strange that moving requirements to test's makes it fail on older versions...
any idea @stancld ?