Spring Update ServletContainerInitializer filename with old javax prefix to jakarta.

Affects: 6.0.0-SNAPSHOT

When implementing the WebApplicationInitializer interface, the implementation is never called. This was caused because this file is still named with the old javax namespace.

As a workaround, I just added the file with the jakarta.servlet.ServletContainerInitializer to my app.

Found that problem while working with Spring Security samples that use the custom WebApplicationInitializer implementation.