[!!!][TASK] Remove security.usePasswordPolicyForFrontendUsers

The feature toggle `security.usePasswordPolicyForFrontendUsers` has
been introduced in TYPO3 12.3 to provide a smooth migration path for
websites using the deprecated TypoScript based password validation
in the password recovery process of ext:felogin.

Since the TypoScript based password validation in ext:felogin has been
removed with #101097, the previously introduced feature toggle has
become obsolete.

This change removes the feature toggle
`security.usePasswordPolicyForFrontendUsers` and all related code.

Resolves: #102023
Related: #97390
Related: #101097
Releases: main
Signed-off-by: Torben Hansen <derhansen@gmail.com>
Change-Id: If09ba49e403fe5e3aaf99d054e0dd9b355a93f24
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/81186


Tested-by: Georg Ringer <georg.ringer@gmail.com>
Reviewed-by: Oliver Klee <typo3-coding@oliverklee.de>
Tested-by: core-ci <typo3@b13.com>
Reviewed-by: Georg Ringer <georg.ringer@gmail.com>
Reviewed-by: Benni Mack <benni@typo3.org>