WIP: Change Restricted Visibility Level description

What does this MR do?

This changes the language for the description test on the Restrict Visibility settings

Similar to !37983 (closed) which aims to clarify the meaning of the checkboxes, this change is to the actual user visible string. Removing the double-negative makes it easier to understand what the settings actually restrict.

I changed the msgid and did a global search-replace for it in all the localization. There's a chance that the translations will make less sense in some languages.

Screenshots

Changed to read:

Restricted levels can only be used by admin users for groups, projects or snippets. If the public level is restricted, user profiles are only visible to logged in users.

This actually rings true with the option in settings.rb as well:

      optional :restricted_visibility_levels, type: Array[String], coerce_with: Validations::Types::CommaSeparatedToArray.coerce, desc: 'Restricted levels can only be used by admin users for groups, projects or snippets. If the public level is restricted, user profiles are only visible to logged in users.'

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers
• Informed Infrastructure department of a default or new setting change, if applicable per definition of done

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• Label as security and @ mention @gitlab-com/gl-security/appsec
• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• Security reports checked/validated by a reviewer from the AppSec team