Previously we set the value of allowIfAllAbstainDecisions to true, this was not ported to the UnanimousStrategy service

[acrobat]

Q	A
Branch?	3.x for new features / the branch of the current release for fixes
Bug fix?	yes
New feature?	no
BC breaks?	no
Deprecations?	no
Fixed tickets
License	MIT
Doc PR	reference to the documentation PR, if any

There was a bc break in the SF6 compatibility fixes in https://github.com/symfony-cmf/core-bundle/pull/285/files#diff-1321e425c72f090b283c6b80c2dc411e7e1d60b47f144ed1b5bf11e04177386fR9. We created the UnanimousStrategy service as string strategy names were deprecated. But the allowIfAllAbstainDecisions value passed to the Symfony\Component\Security\Core\Authorization\AccessDecisionManager was not ported to that service. Resulting in previously having it true and now false. This PR fixes that BC break

[acrobat]

The argument https://github.com/symfony-cmf/core-bundle/pull/292/files#diff-1321e425c72f090b283c6b80c2dc411e7e1d60b47f144ed1b5bf11e04177386fR16 can also be removed, as it is not used anymore. Should I do it in this PR or is that consired a bc break?