Summary:
**Motivation**
This PR fixes the flow type definition of StackFrame in parseErrorStack.js. The methodName was missing and the column could be `null`. We integrate with it in our codebase and we wanted to use `methodName`, but flow complained.
Refer to this file for possible values: [github.com/errwischt/stacktrace-parser/blob/master/lib/stacktrace-parser.js](https://github.com/errwischt/stacktrace-parser/blob/master/lib/stacktrace-parser.js)
This also allowed me to remove a flow error suppression.
**Test plan (required)**
I ran flow on the project, no errors
Closes https://github.com/facebook/react-native/pull/12499
Differential Revision: D4619885
Pulled By: ericvicenti
fbshipit-source-id: 0bf5a2304cb0dc9f2c6df026a5cee71c8a419c01
Marshall Roch
Pieter De Baets
Wietse Venema