Fixes #3136. Update expected errors location in initializer_not_a_constant_t03.dart (#3138)

Update expected errors location in initializer_not_a_constant_t03.dart

Author: sgrekhov

Language/Classes/Constructors/Constant_Constructors/initializer_not_a_constant_t03.dart

@@ -5,6 +5,7 @@
 /// @assertion It is a compile-time error if a constant constructor is declared
 /// by a class C if any instance variable declared in C is initialized with an
 /// expression that is not a constant expression
+///
 /// @description Checks that compile error is produced if class declares a
 /// constant constructor and has instance variable which is initialised by static
 /// non-constant expression.
@@ -24,6 +25,4 @@ class C {
 
 main() {
   const C();
-//      ^
-// [cfe] unspecified
 }