Remove duplicated interfaces

[ohbarye]

Hello maintainers, thanks for the great library.

This PR removes some duplicated interfaces that I found while reading formik's code.

Those interfaces are added in #141 and still remains, but they exist in withFormik.ts as well.

formik/src/withFormik.tsx

Lines 72 to 82 in 095e915

	export type CompositeComponent<P> =
	| React.ComponentClass<P>
	| React.StatelessComponent<P>;
	export interface ComponentDecorator<TOwnProps, TMergedProps> {
	(component: CompositeComponent<TMergedProps>): React.ComponentType<TOwnProps>;
	}
	export interface InferableComponentDecorator<TOwnProps> {
	<T extends CompositeComponent<TOwnProps>>(component: T): T;
	}

[ohbarye]

Thank you for your quick review.