Explicit `Self: Sized` bounds missing from generated documentation.

[jswrenn]

Nearly every method of Iterator has an explicit Self: Sized bound. These bounds are present in libcore's documentation (e.g., Iterator::count), but are missing in libstd's documentation (e.g., Iterator::count).

[dwrensha]

This looks like a dupe of #24183.

[Mark-Simulacrum]

Indeed. Closing as duplicate.