fix(contacts): remove double import of checkAvailability

[paxtonhare]

Fixes #2626

[dschoeni]

This isn't fixed in the newest release - If you download the package using NPM:

https://registry.npmjs.org/@ionic-native/contacts/-/contacts-5.0.0-beta.17.tgz

You can check in the ngx/index.js and index.js file that a double-import still happens:

L17:

import { IonicNativePlugin, checkAvailability, cordovaInstance, instanceAvailability, instancePropertyGet, instancePropertySet, checkAvailability, getPromise } from '@ionic-native/core';

I guess its fixed in the TypeScript sources, but not in the compiled release on NPM?

[JavyMB]

Just like @dschoeni mention, This isn't fixed.
Using NPM:
npm install --save @ionic-native/contacts@5.0.0-beta.18