fix icon theme code style

components/date-picker/RangePicker.tsx

@@ -320,7 +320,7 @@ class RangePicker extends React.Component<any, RangePickerState> {
         type="close-circle"
         className={`${prefixCls}-picker-clear`}
         onClick={this.clearSelection}
-        theme={'filled'}
+        theme="filled"
       />
     ) : null;
 

components/date-picker/WeekPicker.tsx

@@ -115,7 +115,7 @@ class WeekPicker extends React.Component<any, any> {
         type="close-circle"
         className={`${prefixCls}-picker-clear`}
         onClick={this.clearSelection}
-        theme={'filled'}
+        theme="filled"
       />
     ) : null;
     const input = ({ value }: {  value: moment.Moment | undefined }) => {

components/date-picker/createPicker.tsx

@@ -162,7 +162,7 @@ export default function createPicker(TheCalendar: React.ComponentClass): any {
           type="close-circle"
           className={`${prefixCls}-picker-clear`}
           onClick={this.clearSelection}
-          theme={'filled'}
+          theme="filled"
         />
       ) : null;
 

components/rate/index.tsx

@@ -26,7 +26,7 @@ export default class Rate extends React.Component<RateProps, any> {
 
   static defaultProps = {
     prefixCls: 'ant-rate',
-    character: <Icon type="star" />,
+    character: <Icon type="star" theme="filled" />,
   };
 
   private rcRate: any;

components/tree/Tree.tsx

@@ -179,7 +179,7 @@ export default class Tree extends React.Component<TreeProps, any> {
         <Icon
           type={expanded ? 'minus-square' : 'plus-square'}
           className={`${prefixCls}-switcher-line-icon`}
-          theme={'outlined'}
+          theme="outlined"
         />
       );
     } else {