Update Japanese translation

[gemmaro]

Hello RubyGems,

This updates Japanese translation (continuation of #4779).
Each commit adds changes corresponding to those made to the respective English/Japanese file (en.yml/ja.yml), as specified in the commit subject.

Thank you,
gemmaro.

---

TODOs to be ready for review.

• Self-check the translation by looking at the way the messages are called.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 94.36%. Comparing base (94e09f7) to head (4eb4e49).

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #5272      +/-   ##
==========================================
- Coverage   97.13%   94.36%   -2.77%     
==========================================
  Files         457      457              
  Lines        9567     9626      +59     
==========================================
- Hits         9293     9084     -209     
- Misses        274      542     +268     

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[martinemde]

Thank you for all these updates. Do you feel this is ready for review or are there more changes you would like to make?

Should we have someone else check your work? My preference is for merging quickly and then applying fixes quickly but I would also appreciate a Japanese language review if possible.

[gemmaro]

Sorry for the delay. Now it is ready for review (I made some changes to the draft.)

Should we have someone else check your work? My preference is for merging quickly and then applying fixes quickly but I would also appreciate a Japanese language review if possible.

I agree with your approach of merging quickly and then applying fixes quickly.
I hope any corrections will be made later (I'd like to ping @okuramasafumi, and others are welcome to check as well!)