Include reference to Thymeleaf bug

[skagedal]

In the current version of the example (since Migrate to Spring Boot 3.0.0), the following is included in build.gradle:

	//  Temporary explicit version to fix Thymeleaf bug
	implementation 'org.thymeleaf.extras:thymeleaf-extras-springsecurity6:3.1.1.RELEASE'

It would be useful with a reference to what that bug is, so one can know whether it is relevant for a particular use case and to be able to follow it.

[Buzzardo]

@rwinch Can you identify the exact issue in Thymeleaf's issue tracker? It would make sense to let people know which issue it is, and maybe we can remove that comment if it has been fixed. Thanks.

[robertmcnees]

I could not find the reference to the Thymeleaf bug, but I did run the guide locally and can confirm that the additional dependency is still needed. As such, I merged PR #76 and will allow dependabot to continue to manage the version of the temporary dependency for now.