Move profiles/gpg_keys#get_keys to users#gpg_keys

What does this MR do?

Moves profiles/gpg_keys#get_keys, introduced in !48321 (merged), to users#gpg_keys with keeping GPG Keys of the user publicly accessible.

This is to profiles/gpg_keys#get_keys what !48991 (merged) is to profiles/keys#get_keys.

security & ~"technical debt": All Profiles::*Controllers are designed only for operations the logged-in and own user. Having skip_before_action :authenticate_user! to some action there can potentially be a security hole.

This does not change any specs except for renaming profiles/gpg_keys#get_keys to users#gpg_keys.

Screenshots (strongly suggested)

n/a

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Code review guidelines
• Style guides
• Separation of EE specific content

Closes #290762 (closed)