wp_kses() et al. $allowed_html parameter not documented as accepting string values

[jdgrimes]

Since [21790] as part of 3.5.0, wp_kses() and some of its companion functions have accepted a string as the value of the $allowed_html parameter, which is then expanded to an array as needed using wp_kses_allowed_html(). However, these functions are still documented as only accepting an array for $allowed_html. The inline docs for them need to be updated to indicate that a string is also accepted. Probably they should reference wp_kses_allowed_html(), where the possible values are documented.

[Christian1012]

First pass added in 39542.0.diff

[markparnell]

Looks like this was updated in [43016].

[SergeyBiryukov]

In 48478:

Docs: Synchronize description for the $allowed_html parameter of various KSES functions.

Follow-up to [43016].

Props Christian1012, jdgrimes, markparnell.
Fixes #39542. See #33801.