Revert "parent-pom: Update to Spring-Boot 2.6.7"
Revert "parent-pom: Update to Spring-Boot 2.6.7"

This reverts commit dd0e548d6f1301bfd81a00de323da22336e8065c.

Reason: Spring Boot >= 2.4 breaks due to errors launching Tomcat.
This requires more investigation, but it seems that we're stuck on
Spring Boot 2.3 for now.

Possibly related: Spring Boot 2.4 Release Notes mention this:

https://github.com/spring-projects/spring-boot/wiki/Spring-Boot-2.4-Release-Notes#register-weblisteners-in-a-way-that-allows-them-to-register-servlets-and-filters

> A side-effect of this change is that the Servlet container now
> creates the instance of the WebListener and, therefore, dependency
> injection such as with @Autowired can no longer be used. In such
> cases, @Component should be used instead.

Not sure if this is the cause of the problems, but worth noting
it here.

Kurento/kurento-java,Kurento/kurento-java,Kurento/kurento-java,Kurento/kurento-java