Spring Security WebSessionServerCsrfTokenRepository#generateToken() don't use Schedulers.boundedElastic()

Describe the bug

in master branch, Schedulers.boundedElastic() is not used because the Mono chain is broken.

https://github.com/spring-projects/spring-security/blob/57c5ec26e7af1a4c2b8da894840fe55bf6897b9f/web/src/main/java/org/springframework/security/web/server/csrf/WebSessionServerCsrfTokenRepository.java#L53-L57

To Reproduce

Call WebSessionServerCsrfTokenRepository#generateToken().

Expected behavior

Use Schedulers.boundedElastic() .

Sample

N/A

I think I need to revert back to 8866fa6fb065b206724f36d1c9ee1d6bee46a4bd:

https://github.com/spring-projects/spring-security/blob/8866fa6fb065b206724f36d1c9ee1d6bee46a4bd/web/src/main/java/org/springframework/security/web/server/csrf/WebSessionServerCsrfTokenRepository.java#L53-L55