Remove springfox from dependencies

Please check if the PR fulfills these requirements (please use '[x]' to check the checkboxes, or submit the PR and then click the checkboxes)

[X] The commit message follows our guidelines
[ ] Tests for the changes have been added (for bug fixes / features)
[ ] Docs have been added / updated (for bug fixes / features)

What kind of change does this PR introduce? (Bug fix, feature, docs update, ...)

Bugfix / technical debt.

What is the current behavior? (You can also link to an open issue here)

Springfox does not work with recent spring-boot versions, and may stop user applications from starting.

What is the new behavior (if this is a feature change)?

Users can restore the configuration on their side if they really need it. It was not a good design to include it in the spring module: applications should be in charge of it.

In any case, the use of springdoc is now encouraged instead.

powsybl / powsybl-afs

Remove springfox from dependencies #118