style: convert single quotes to back quotes

[JTNEX]

Close #2232 This commit changed the single quotes to back quotes where they were used in the Markdown.

Pull request checklist

• [x] The PR has a proper title. Use Semantic Commit Messages. (No more branch-name title please)
• [x] Make sure this is ready to be merged into the relevant branch. Please don't create a PR and let it hang for a few days.
• [x] Ensure you can run the codes you submitted succesfully. These submissions will be prioritized for review:

PR type

• Bug fix
  • (like a typo)

Description

In the Japanese README, there were some parts where the Markdown format was not correctly written. I corrected the formatting by replacing the single quotes with back quotes.

Screenshot

• before

• after