Allow Symfony 7

[andrewmy]

Let's install this on modern apps too!

• Allow Symfony ^7.0 in the composer requirements;
• Add Symfony 7.0.* to the CI matrix.

[andrewmy]

Oops, I see the 5.0 branch now 🙈

[malarzm]

@andrewmy: appreciating the energy! 🍻

[bitgandtter]

i don't see this changes here https://github.com/doctrine/DoctrineMongoDBBundle/blob/4.7.x/composer.json intended to upgrade sf to 7.x