docs: Fixed name of uses-permission-sdk-23

Docs had incorrectly said the element was named
<uses-permission-sdk23> (missing a hyphen in sdk-23). Fixing all
references to that element, and renaming the reference page
accordingly. A separate CL sets up a redirect from the old page
name to the new one.

See first comment for doc stage location.

Change-Id: I6e675e03f87851d36465a8fdf3de730de524c4a8
bug: 25346975