Update codeowners that don't need wildcards

What does this MR do and why?

While working on an MR that I knew should be covered by a codeowners entry, I noticed that there was no approval rule for it. Reviewing the codeowners entry shows that we are using /doc-locale/**, but the docs do not mention this format: https://docs.gitlab.com/user/project/codeowners/reference/

It seems ** should only be used for directory wildcards, like path/**/index.md. To cover all files in a directory, just end in /: https://docs.gitlab.com/user/project/codeowners/reference/#directory-paths

This MR removes the ** from all CODEOWNERS entries that are meant to cover all files in a directory. Ex: /path/** -> /path/

References

Screenshots or screen recordings

File changed in MR:

doc-locale/ja-jp/ci/testing/test_coverage_visualization/_index.md

Entry in CODEOWNERS:

[Localization Team] @gitlab-com/localization/maintainers
/doc-locale/**

View in MR:

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