Cleanup kotlin sources

1. remove unused import
2. remove redundant semicolon
3. remove redundant empty constructor and SAM-constructor
4. remove unnecessary type argument
5. adjust indent

See gh-31913

spring-aop/src/test/kotlin/org/springframework/aop/support/AopUtilsKotlinTests.kt

@@ -46,7 +46,7 @@ class AopUtilsKotlinTests {
     @Suppress("unused")
     suspend fun suspendingFunction(value: String): String {
         delay(1)
-        return value;
+        return value
     }
 
 }