ITunesGenerator `explicit` tag should be true/false instead of yes/no

[aurelman]

Hello,

Topic

As per Itunes documentation there https://podcasters.apple.com/support/5440-explicit-content
The explicit value should be one of true or false, instead of yes / no for channels and items.

[antoniosanct]

https://help.apple.com/itc/podcasts_connect/#/itcb54353390