Update javadoc of HttpSecurity, WebSecurityConfiguration and WebSecurity to reflect deprecation of WebSecurityConfigurerAdapter

[jonathanlermitage]

WebSecurityConfigurerAdapter has been deprecated in Spring Security 5.7 but the javadoc of the following classes still encourages its use:

• HttpSecurity:

  spring-security/config/src/main/java/org/springframework/security/config/annotation/web/builders/HttpSecurity.java

  Lines 117 to 128 in 4caf53e

  	* public class FormLoginSecurityConfig extends WebSecurityConfigurerAdapter {
  	*
  	* @Override
  	* protected void configure(HttpSecurity http) throws Exception {
  	* http.authorizeRequests().antMatchers("/**").hasRole("USER").and().formLogin();
  	* }
  	*
  	* @Override
  	* protected void configure(AuthenticationManagerBuilder auth) throws Exception {
  	* auth.inMemoryAuthentication().withUser("user").password("password").roles("USER");
  	* }
  	* }

• WebSecurityConfiguration:

  spring-security/config/src/main/java/org/springframework/security/config/annotation/web/configuration/WebSecurityConfiguration.java

  Line 57 in 4caf53e

  * can be made to {@link WebSecurity} by extending {@link WebSecurityConfigurerAdapter}

• and WebSecurity:

  spring-security/config/src/main/java/org/springframework/security/config/annotation/web/builders/WebSecurity.java

  Line 80 in 4caf53e

  * {@link WebSecurityConfigurer}, overriding {@link WebSecurityConfigurerAdapter} or