[TextField] Focused prop is not setting focus on the element

[amireynoso]

Issue summary

The focused prop on the <TextField /> component is not setting focus on the input.

Expected behavior

When focused is set to true, the input (or textarea if multiline is set) should be on its focus state.

Actual behavior

The input/textarea is on its default state.

Steps to reproduce the problem

1. Create a <TextField /> with the focused prop set to true
2. Verify the input is not on its focus state

Reduced test case

https://codesandbox.io/s/n41rrjovl0?module=App.js

Specifications

• Are you using the React components? (Y/N): Yes
• Polaris version number: 3.6.0
• Browser: Google Chrome 71.0.3578.98
• Device: MacBook Pro
• Operating System: macOS Mojave 10.14.2

[ghost]

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