Revert "Fix DDB Enhanced Client immutable class introspection fails for "is" prefix fields"

.changes/next-release/bugfix-DynamoDBEnhancedClient-6fa9afe.json

@@ -0,0 +1,6 @@
+{
+    "type": "bugfix",
+    "category": "DynamoDB Enhanced Client",
+    "contributor": "",
+    "description": "Revert problematic change from [#6349](https://github.com/aws/aws-sdk-java-v2/issues/6349)."
+}

services-custom/dynamodb-enhanced/src/main/java/software/amazon/awssdk/enhanced/dynamodb/internal/immutable/ImmutableIntrospector.java

@@ -180,14 +180,6 @@ private String normalizeSetterName(Method setter) {
             return Character.toLowerCase(setterName.charAt(3)) + setterName.substring(4);
         }
 
-        if (setterName.length() > 2
-            && Character.isUpperCase(setterName.charAt(2))
-            && setterName.startsWith(IS_PREFIX)
-            && isSetterMethodBoolean(setter)) {
-
-            return Character.toLowerCase(setterName.charAt(2)) + setterName.substring(3);
-        }
-
         return setterName;
     }
 
@@ -216,11 +208,6 @@ private boolean isMethodBoolean(Method method) {
         return method.getReturnType() == boolean.class || method.getReturnType() == Boolean.class;
     }
 
-    private boolean isSetterMethodBoolean(Method setter) {
-        return setter.getParameterCount() == 1 && 
-               (setter.getParameterTypes()[0] == boolean.class || setter.getParameterTypes()[0] == Boolean.class);
-    }
-
     private Optional<Method> extractBuildMethod(Map<String, Method> indexedBuilderMethods, Class<?> immutableClass) {
         Method buildMethod = indexedBuilderMethods.get(BUILD_METHOD);