[3.11] typing docs: Move some classes out of the "Generics" section (GH-104707) ...

[3.11] typing docs: Move some classes out of the "Generics" section (GH-104707) (#104721)

- AnyStr can be used in type annotations, contrary to the section header
- Unpack can also be used in annotations, and its use is not restricted
  to generics. It makes more sense with other building blocks like Required.
- Protocol is not necessarily generic.

Also fix the indentation for two notes associated with Concatenate.

(cherry picked from commit ab71acd67b5b09926498b8c7f855bdb28ac0ec2f)

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Co-authored-by: Alex Waygood <Alex.Waygood@Gmail.com>