tighten EdgeInsetsPropType flow type

Reviewed By: yungsters

Differential Revision: D6767104

fbshipit-source-id: 40b1a4f9f41ff4beae141b636738994ccfa96d37

Author: sahrens

Libraries/StyleSheet/EdgeInsetsPropType.js

@@ -22,11 +22,11 @@ const EdgeInsetsPropType = (createStrictShapeTypeChecker({
   right: PropTypes.number,
 }): ReactPropsCheckType & ReactPropsChainableTypeChecker);
 
-export type EdgeInsetsProp = {
-  top: number,
-  left: number,
-  bottom: number,
-  right: number,
-};
+export type EdgeInsetsProp = {|
+  +top: number,
+  +left: number,
+  +bottom: number,
+  +right: number,
+|};
 
 module.exports = EdgeInsetsPropType;