[Demo] Remove --strict to composer validate (using @dev for now on deps)

[fabpot]

Q	A
Bug fix?	no
New feature?	no
Docs?	no
Issues	n/a
License	MIT

As we're using unbounded deps for now (@dev), we cannot use --strict on composer validate.

[fabpot]

I'm not even sure this pipeline entry in composer.json is useful. AFAICS, it's not used anywhere and the php-cs-fixer line doesn't work either as there is no directory and no PHPCSFixer configuration file. As it's not used in the Github action workflows, maybe we can just remove it? @chr-hertel

[chr-hertel]

That's mostly a left over from the demo being a standalone repository - missed to remove it, true

[fabpot]

ok, removed.

[chr-hertel]

Thank you @fabpot.