Rate limits: Cross-link docs and tweak UI wording

What does this MR do?

Cross-link rate limit docs and tweak UI wording.

From #29952 (comment 241670651):

I've added a couple small to do items.

• Remove A web server restart is required after changing these settings.

I believe the new Admin Area Protected Paths don't need a web server restart.

I believe Omnibus Protected Paths require a restart because you modify gitlab.rb then reconfigure, which regenerates the initializer, which must be loaded again.

• Change Omnibus Protected Paths throttle is active. to Omnibus Protected Paths throttle is active, and takes priority over these settings.

Since it doesn't matter whether the Admin Area settings are enabled or not, when this message is being displayed.

Screenshots

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