Use the same shade of grey in both dash and question lists

frontend/src/metabase/dashboards/containers/Dashboards.jsx

@@ -144,9 +144,8 @@ export class Dashboards extends Component {
 
         return (
             <LoadingAndErrorWrapper
-                style={{ backgroundColor: "#f9fbfc" }}
                 loading={isLoading}
-                className={cx("relative px4 full-height", {"flex flex-full flex-column": noDashboardsCreated})}
+                className={cx("relative px4 full-height bg-slate-extra-light", {"flex flex-full flex-column": noDashboardsCreated})}
                 noBackground
             >
                 { modalOpen ? this.renderCreateDashboardModal() : null }

frontend/src/metabase/questions/containers/QuestionIndex.jsx

@@ -111,7 +111,7 @@ export class QuestionIndex extends Component {
         const showEverythingElseTitle = hasQuestionsWithoutCollection && hasCollections;
 
         return (
-            <div className={cx("relative mx4", {"full-height flex flex-column": showNoSavedQuestionsState})}>
+            <div className={cx("relative px4", {"full-height flex flex-column bg-slate-extra-light": showNoSavedQuestionsState})}>
                 { showNoCollectionsState && <CollectionEmptyState /> }
 
                 <QuestionIndexHeader