[ja] Update blog content files to move translator details in front-matter

[Okabe-Junya]

Change List

• In #47270, we're updating the blog to manage "translator(s)" as metadata. Some blogs localized into Japanese already have a "translator" set, so migrate those.

Note

unhold this once #47270 is merged.

useful links

• Blog Summary (not changed): link
• Blog Article page (add "Translate By"): Before | After

/hold