Simplify boolean expression

Simplify boolean expression of the form `if (b == true)` to instead
just use the form `if (b)`.

Issue gh-8945

config/src/main/java/org/springframework/security/config/http/HeadersBeanDefinitionParser.java

@@ -234,7 +234,7 @@ public class HeadersBeanDefinitionParser implements BeanDefinitionParser {
 				headersWriter.addPropertyValue("preload", preload);
 			}
 
-			if (disabled == true) {
+			if (disabled) {
 				return;
 			}
 		}

etc/checkstyle/checkstyle-suppressions.xml

@@ -3,7 +3,6 @@
 		"-//Checkstyle//DTD SuppressionFilter Configuration 1.2//EN"
 		"https://checkstyle.org/dtds/suppressions_1_2.dtd">
 <suppressions>
-	<suppress files=".*" checks="SimplifyBooleanExpression" />
 	<suppress files=".*" checks="SimplifyBooleanReturn" />
 	<suppress files=".*" checks="SpringAvoidStaticImport" />
 	<suppress files=".*" checks="SpringCatch" />