Improve inline documention for `set_transient()` and `set_site_transient()` to specify the 45- and 40-character limits for their respective transient name values.

Props edwin-at-studiojoyo.com for the original patch.
See #15058, #13310. Fixes #28467.


git-svn-id: https://develop.svn.wordpress.org/trunk@28735 602fd350-edb4-49c9-b593-d223f7449a82