Table Search Accessibility

Aria-label is being applied to 'div' instead of the 'input'

## Expected Behavior
In the table search component, the `input` should have `aria-label="Search"` or equivalent.

## Current Behavior
In the table search component, the `aria-label` is being applied to the `div` that contains the `input` rather than on the `input` itself.

## Steps to Reproduce (for bugs)

1. Any table with contents and an active search input
2. Inspect the `input` element and its containing `div`

## Your Environment

| Tech | Version |
|--------------|---------|
| Material-UI | 3.x |
| MUI-datatables | 2.13.3 |
| React | 16.12.0 |
| browser | Chrome 79.0.3945.117 |

The issue does not name a file or test; start by locating the table search component and inspect the rendered input and its containing div. Verify the change by checking that the input, rather than its div, exposes aria-label="Search" in the DOM.

Written by the indexing model from the issue text.