Report syntax error on unescaped annotation

Also adjust parser testData

compiler/testData/psi/primaryConstructor/valid.kt

@@ -6,8 +6,10 @@ private constructor(y: Int) : Base1(), Base2 {
 }
 class A2 @private constructor(y: Int)
 
-class A3 Ann(1) private constructor(y: Int)
+class A3 @Ann(1) private constructor(y: Int)
 
-class A4 private Ann(1) constructor(y: Int)
+class A4 private @Ann(1) constructor(y: Int)
 
 class A5 @Ann private constructor() {}
+
+class A6 Ann() private constructor() {}