Drop support for symfony 4.4

[maelanleborgne]

Symfony 4.4 is coming to the end of it's security fix support, it is not recommended to use this version anymore, 5.4 is the current LTS version and 6.4 is just around the corner.
I'd be happy to drop 4.4 support and release a new version so that 4.4 users can keep using this bundle in it's 1.1.0 version, while we add new updates for 5.4 / 6.* / 7.0 only.
That will make it easier for developers who want to contribute, since juggling with compatibility isn't easy (and there's a big gap between 4.4 and 7.0).

[ThomasLandauer]

Ping @isometriks This is more urgent now, since Symfony 7.0 was released already.