Update webauthn4j version in webauthn4j-spring-security

[TGITS]

Update webauthn4j-spring-security to the latest version of webauthn4j published on maven central.

The update from 0.20.6 to 0.20.7 was surprisingly tricky due to the use by spring 2.7.x of a version 1.7.x of SL4J
(with the related 1.2.x version of logback)

For the time being mark as draft PR :

• the solution to correct the problem with the tests is only a workaround, there is maybe a better solution, and in any case, the problem may need further discussion.
• For now the version 0.20.8 of WebAuthn4j is not on Maven central for the first version of this PR but it will maybe come soon, and thus we can potentially directly update to the version 0.20.8.

[ynojima]

Thank you for your suggestion.
It seems it's root cause is webauthn4j-core and webauthn4j-util specify logback version unnecessarily in their poms. (webauthn4j-core and webauthn4j-util use logback in test module only.)
I'll fix it in the next webauthn4j version, but I'll merge this patch into webauthn4j-spring-security.