Tweak a sentence in Japanese documentation

[seratch]

Summary

This pull request improves the quality of Japanese documentation. The current comment seems to be a bit confusing. The new one is much closer to the original sentence: You could also set userToken instead.

Just in case, I've assigned @girliemac (another Japanese speaker in the team) as a reviewer but I may self merge after waiting for her response for a while.

Requirements (place an x in each [ ])

• I've read and understood the Contributing Guidelines and have done my best effort to follow them.
• I've read and agree to the Code of Conduct.

[codecov]

Codecov Report

Merging #363 into master will not change coverage.
The diff coverage is n/a.

@@          Coverage Diff          @@
##           master   #363   +/-   ##
=====================================
  Coverage      73%    73%           
=====================================
  Files           7      7           
  Lines         500    500           
  Branches      146    146           
=====================================
  Hits          365    365           
  Misses        103    103           
  Partials       32     32

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