fix(android): use function vs arrow for babel compat in AppleButton export (#234)

Use function syntax instead of arrow function

Author: EIrwin

lib/AppleButton.android.js

@@ -7,7 +7,7 @@ import { ButtonTexts, ButtonTypes, ButtonVariants } from './AppleButton.shared';
  * Pure Javascript Apple Sign In button for Android.
  * Cross-compatible with native iOS version.
  */
-export default AppleButton = (props) => {
+export default function AppleButton(props) {
   const {
     style,
     textStyle,