[TASK] Remove dependency to webmozart/assert

TYPO3 uses "phpdocumentor/reflection-docblock" (added in Jan 2019)
but also added "webmozart/assert" which is not needed directly (as it is
a subdependency). Thus, TYPO3 Core should only require what is directly
used, therefore the dependency is removed.

Used composer command:
  composer remove webmozart/assert

Resolves: #90364
Releases: master
Change-Id: Ief2787cb98c0080517f73e321ab34568b0addafb
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/63209


Tested-by: Georg Ringer <georg.ringer@gmail.com>
Tested-by: Benni Mack <benni@typo3.org>
Reviewed-by: Georg Ringer <georg.ringer@gmail.com>
Reviewed-by: Benni Mack <benni@typo3.org>