Fix a missing "throws Exception" for configure(AuthenticationManagerBuilder auth)

The actual method signature look this this:
```java
protected void configure(AuthenticationManagerBuilder auth) throws Exception
```
 This PR aims at aligning the javadoc for this annotation with the actual method signature.

config/src/main/java/org/springframework/security/config/annotation/web/configuration/EnableWebSecurity.java

@@ -52,7 +52,7 @@ import org.springframework.security.config.annotation.web.WebSecurityConfigurer;
  * 	}
  *
  * 	@Override
- * 	protected void configure(AuthenticationManagerBuilder auth) {
+ * 	protected void configure(AuthenticationManagerBuilder auth) throws Exception {
  * 		auth
  * 		// enable in memory based authentication with a user named "user" and "admin"
  * 		.inMemoryAuthentication().withUser("user").password("password").roles("USER")