Remove old splitter controls from the workbench.

lib/ReactViews/Workbench/WorkbenchItem.jsx

@@ -23,7 +23,6 @@ import DateTimeSelectorSection from "./Controls/DateTimeSelectorSection";
 import DimensionSelectorSection from "./Controls/DimensionSelectorSection";
 import DisplayAsPercentSection from "./Controls/DisplayAsPercentSection";
 import FilterSection from "./Controls/FilterSection";
-import LeftRightSection from "./Controls/LeftRightSection";
 import Legend from "./Controls/Legend";
 import OpacitySection from "./Controls/OpacitySection";
 import SatelliteImageryTimeFilterSection from "./Controls/SatelliteImageryTimeFilterSection";
@@ -167,7 +166,6 @@ export const WorkbenchItemRaw = observer(
                 viewState={this.props.viewState}
               />
               <OpacitySection item={workbenchItem} />
-              <LeftRightSection item={workbenchItem} />
               <TimerSection item={workbenchItem} />
               <If
                 condition={

lib/ReactViews/Workbench/WorkbenchList.jsx

@@ -2,7 +2,6 @@ import React from "react";
 import PropTypes from "prop-types";
 import Sortable from "react-anything-sortable";
 
-import WorkbenchSplitScreen from "./WorkbenchSplitScreen";
 import WorkbenchItem from "./WorkbenchItem";
 import { observer } from "mobx-react";
 import { action } from "mobx";
@@ -28,9 +27,6 @@ class WorkbenchList extends React.Component {
   render() {
     return (
       <ul className={Styles.workbenchContent}>
-        {this.props.terria.showSplitter && (
-          <WorkbenchSplitScreen terria={this.props.terria} />
-        )}
         <Sortable onSort={this.onSort} direction="vertical" dynamic={true}>
           <For each="item" of={this.props.terria.workbench.items}>
             <WorkbenchItem