Update Javadoc for mocks regarding Servlet 3.0

Commit deba32cad9 upgraded the Servlet API mocks to Servlet 3.0;
however, not all of the Javadoc was updated accordingly.

This commit updates the remaining Javadoc with regard to Servlet 3.0 as
the baseline for mocks in the spring-test module.

In addition, this commit syncs up the mocks used for internal testing in
the spring-web module with the most current versions from spring-test.

Issue: SPR-11049