Fix some PHPStan errors

[jmsche]

Q	A
PHP version?	N/A
Bundle version?	0.10.2
Symfony version?	N/A
New feature?	no
Bug fix?	kind of
Discussion?	N/A

Fixing some PHPStan errors.

Not sure what's the best way to fix remaining DBAL (schema-related) & PHPUnit (withConsecutive() call) deprecations, so leaving them for now.

[Guikingone]

Hi @jmsche 👋🏻

As this PR update the dbal version, I think it could be a better idea to add it in 0.11 or 1.0 if that's good for you?

[jmsche]

Sure :) As the bundle is still in v0.x version, it may be okay to release it for next 0.x version.

Just converted the PR to draft, as I found a (long) way to fix the withConsecutive() calls :)