findBreakingChanges: Remove 'export' from internal functions

[IvanGoncharov]

Note: Only functions exported by index.js are treated as part of
Public API

graphql-js/src/utilities/index.js

Lines 124 to 130 in c0cf659

	// Compares two GraphQLSchemas and detects breaking changes.
	export {
	BreakingChangeType,
	DangerousChangeType,
	findBreakingChanges,
	findDangerousChanges,
	} from './findBreakingChanges';