[ja] Fix broken link

[polamjag]

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This pull request makes a minor formatting correction to the Japanese documentation.

Specifically I fixed the use of parentheses in Markdown links to ensure the correct type is used (They must be half-width, not full-width, to work as Markdown links).

[linux-foundation-easycla]

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• ✅ login: polamjag / name: Satoru Abe (2fcbbc4)