Deprecated hint on BasicAuthenticationFilter

[mczul]

Hi Spring Security Team,

first of all: Thanks for your effort and your amazing work!

I recently read through the JavaDoc of BasicAuthenticationFilter and was a bit irritated by lines 84 to 86 where Digest Auth was described as a better alternative for Basic Auth which is certainly a deprecated artifact and conflicts with the warning stated on the official tutorial.

It's not a big deal for readers with basic security knowledge... but maybe unsophisticated project setups can be prevented if deprecated hints like this are removed.

spring-security/web/src/main/java/org/springframework/security/web/authentication/www/BasicAuthenticationFilter.java

Lines 84 to 86 in 9ec3e80

	* undesirable in many situations. Digest authentication is also provided by Spring
	* Security and should be used instead of Basic authentication wherever possible. See
	* {@link org.springframework.security.web.authentication.www.DigestAuthenticationFilter}.

[jzheaux]

Good catch, @mczul! Can you provide a PR to update the JavaDoc? And would you please base that change on 5.7.x?