Atan2() missing from Math Expression node

Using the math expression Atan2(y,x) inside of a math expression node results in an error. 

Tested in:  4.23.1 CL#9631420 ,  4.25 CL#11341939

1. Open a 4.24 project
2. Create an actor blueprint
3. Add a math expression node in the event graph.
4. In math expression, use the expression atan2(y,x)

Result: Error appears on the node, atan2 can't be found

Expected: Atan2(y,x) to work as an expression