Fix redirect links in processes/managing-reviewers.md

[tuminoid]

The link checker found URLs that redirect to new locations. These should be updated to point directly to the correct URLs:

Current URL	Redirects To
https://github.com/metal3-io/community/blob/main/maintainers/	https://github.com/metal3-io/community/tree/main/maintainers

Related to #601

/triage accepted
/help
/good-first-issue

[metal3-io-bot]

@tuminoid:
This request has been marked as suitable for new contributors.

Please ensure the request meets the requirements listed here.

If this request no longer meets these requirements, the label can be removed
by commenting with the /remove-good-first-issue command.

In response to this:

The link checker found URLs that redirect to new locations. These should be updated to point directly to the correct URLs:

Current URL	Redirects To
https://github.com/metal3-io/community/blob/main/maintainers/	https://github.com/metal3-io/community/tree/main/maintainers

Related to #601

/triage accepted
/help
/good-first-issue

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes-sigs/prow repository.

[ahmed-kaif]

Hi, here is the PR #627
This is my first PR, please feel free to provide comments/feedback. Thanks

[tuminoid]

/assign @ahmed-kaif