[lint] Add lint rule enforcing React Fragment shorthand (#8585)

superset/assets/src/SqlLab/components/App.jsx

@@ -109,10 +109,10 @@ class App extends React.PureComponent {
       );
     } else {
       content = (
-        <React.Fragment>
+        <>
           <QueryAutoRefresh />
           <TabbedSqlEditors />
-        </React.Fragment>
+        </>
       );
     }
     return (

superset/assets/src/SqlLab/components/ExploreResultsButton.jsx

@@ -184,7 +184,7 @@ class ExploreResultsButton extends React.PureComponent {
   render() {
     const allowsSubquery = this.props.database && this.props.database.allows_subquery;
     return (
-      <React.Fragment>
+      <>
         <Button
           bsSize="small"
           onClick={this.onClick}
@@ -198,7 +198,7 @@ class ExploreResultsButton extends React.PureComponent {
             this.dialog = el;
           }}
         />
-      </React.Fragment>
+      </>
     );
   }
 }

superset/assets/src/SqlLab/components/ResultSet.jsx

@@ -213,7 +213,7 @@ export default class ResultSet extends React.PureComponent {
           ? results.expanded_columns.map(col => col.name)
           : [];
         return (
-          <React.Fragment>
+          <>
             {this.renderControls.bind(this)()}
             {sql}
             <FilterableTable
@@ -223,7 +223,7 @@ export default class ResultSet extends React.PureComponent {
               filterText={this.state.searchText}
               expandedColumns={expandedColumns}
             />
-          </React.Fragment>
+          </>
         );
       } else if (data && data.length === 0) {
         return <Alert bsStyle="warning">{t('The query returned no data')}</Alert>;

superset/assets/src/SqlLab/components/TabbedSqlEditors.jsx

@@ -238,10 +238,10 @@ class TabbedSqlEditors extends React.PureComponent {
       const state = latestQuery ? latestQuery.state : '';
 
       const title = (
-        <React.Fragment>
+        <>
           <TabStatusIcon onClose={() => this.removeQueryEditor(qe)} tabState={state} />{' '}
           {qe.title}{' '}
-        </React.Fragment>
+        </>
       );
       const tabTitle = (
         <SplitButton