Remove ./src/core proxy module.

src/core/index.js

@@ -1 +0,0 @@
-module.exports = require('@uppy/core')

src/core/index.test.js

@@ -1,10 +0,0 @@
-const Core = require('./index')
-
-describe('core/index', () => {
-  it('should expose the uppy core as the default export', () => {
-    expect(typeof Core).toEqual('function')
-    const core = new Core({})
-    expect(typeof core).toEqual('object')
-    expect(core.constructor.name).toEqual('Uppy')
-  })
-})