[1.7.x] Fixed #23530 -- Specified PyYAML requirement in initial-data.txt

Thanks aks for the report.
Backport of 5bf654e44b7 from master.
[1.7.x] Fixed #23529 -- Replaced comments tag library with humanize in docs

Backport of ee442e97da390b7136dc12b66ddfa70263a60b5c from master.
[1.7.x] Fixed #23512 -- Made migration docs about initial_data clearer

Thanks @abhillman and @Markush2010 for submitting the ticket.

Backport of 21819e6dbf422fe3ebe23cc006c0ef7bfc5c73de from master.