[TASK] Raise recommended max nesting level

Raise recommended max nesting level to 400 as 
the current value of 250 does not suffice.

Resolves: #59391
Releases: 6.3, 6.2
Change-Id: Ibccb61991809e24baddb21bd46f190cd0b8d907d
Reviewed-on: https://review.typo3.org/30919
Reviewed-by: Markus Klein
Tested-by: Markus Klein