Support `sensio/framework-extra-bundle:^6`

[Ocramius]

This is mostly a placeholder, potentially fixed by @dependabot upgrades (see #16 (review)), but in:

uuid-extra-bundle/composer.json

Lines 10 to 11 in 3744cf9

	"symfony/framework-bundle": "^3.0|^4.0|^5.0",
	"sensio/framework-extra-bundle": "^3.0|^4.0|^5.0",

It would be a good idea to:

• add symfony/*:^6 support
• drop symfony/*:^3 and symfony/*:^4 support (old versions still work, no?)

[mcfedr]

closed by #18