Move styles for groupby fill container into stylesheet

ui/src/shared/components/FieldList.js

@@ -92,7 +92,7 @@ class FieldList extends Component {
         <div className="query-builder--heading">
           <span>Fields</span>
           {hasAggregates
-            ? <div style={{display: 'flex', alignItems: 'center'}}>
+            ? <div className="query-builder--groupby-fill-container">
                 <GroupByTimeDropdown
                   isOpen={!hasGroupByTime}
                   selected={groupBy.time}

ui/src/style/components/query-builder.scss

@@ -204,3 +204,8 @@
 .query-builder--db-dropdown {
   display: inline-block;
 }
+/* Container for group by and fill dropdowns to live side-by-side */
+.query-builder--groupby-fill-container {
+  display: flex;
+  alignItems: center;
+}