update proptypes according to flow

Author: drewvolz

source/views/components/cells/textfield.js

@@ -32,6 +32,7 @@ export class CellTextField extends React.Component {
     _ref: () => {},
     returnKeyType: 'default',
     secureTextEntry: false,
+    autoCapitalize: 'none',
   }
 
   props: {
@@ -79,7 +80,7 @@ export class CellTextField extends React.Component {
         cellAccessoryView={
           <TextInput
             ref={this.cacheRef}
-            autoCapitalize={this.props.autoCapitalize || 'none'}
+            autoCapitalize={this.props.autoCapitalize}
             autoCorrect={false}
             clearButtonMode="while-editing"
             disabled={this.props.disabled}