RN: Delete TextInput.selectionState Prop

Summary:
Deletes the `selectionState` prop from `TextInput`.

It does not provide meaningful value over `onBlur`, `onFocus`, and `selectionState`.

Changelog:
[Breaking][TextInput] Removing `selectionState` prop, use `onBlur`, `onFocus`, and `onUpdate` instead.

Reviewed By: zackargyle, TheSavior

Differential Revision: D17879667

fbshipit-source-id: 03a4e239406932adad898d6d2a092e3bc2e6b064

Libraries/DeprecatedPropTypes/DeprecatedTextInputPropTypes.js

@@ -12,7 +12,6 @@
 
 const DeprecatedColorPropType = require('./DeprecatedColorPropType');
 const DeprecatedViewPropTypes = require('./DeprecatedViewPropTypes');
-const DocumentSelectionState = require('../vendor/document/selection/DocumentSelectionState');
 const PropTypes = require('prop-types');
 const Text = require('../Text/Text');
 
@@ -388,22 +387,6 @@ module.exports = {
    * The highlight and cursor color of the text input.
    */
   selectionColor: DeprecatedColorPropType,
-  /**
-   * An instance of `DocumentSelectionState`, this is some state that is responsible for
-   * maintaining selection information for a document.
-   *
-   * Some functionality that can be performed with this instance is:
-   *
-   * - `blur()`
-   * - `focus()`
-   * - `update()`
-   *
-   * > You can reference `DocumentSelectionState` in
-   * > [`vendor/document/selection/DocumentSelectionState.js`](https://github.com/facebook/react-native/blob/master/Libraries/vendor/document/selection/DocumentSelectionState.js)
-   *
-   * @platform ios
-   */
-  selectionState: (PropTypes.instanceOf(DocumentSelectionState): void),
   /**
    * The start and end of the text input's selection. Set start and end to
    * the same value to position the cursor.