[TASK] Drop superfluous `conditionContextDefinition` usages

With #86196, usage of the Symfony expression language was streamlined
in core. This also affected EXT:form, since it uses the expression
language for form variants. The form prototype configuration
`conditionContextDefinition` was replaced by an appropriate
configuration using a `Configuration/ExpressionLanguage.php` file.
However, some usages of mentioned form prototype configuration were not
removed.

This patch removes all remaining occurrences of
`conditionContextDefinition` and updates the documentation
accordingly - since this seems to be forgotten with #86196.

Resolves: #97023
Related: #86196
Releases: main, 11.5
Change-Id: If6a7a2b5f5f38326eb1fe9fe339ca7ffeb4bc8e8
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/74942


Tested-by: core-ci <typo3@b13.com>
Tested-by: Elias Häußler <e.haeussler@familie-redlich.de>
Tested-by: waldhacker <hello@waldhacker.dev>
Reviewed-by: Elias Häußler <e.haeussler@familie-redlich.de>
Reviewed-by: waldhacker <hello@waldhacker.dev>