Graph/Legend: Include pivot variant for growthAdvantage

The model JSONs will include GA values for the pivot variant as of
<nextstrain/forecasts-ncov#127>. Update the
Graph's xDomain and the Legend to include the pivot variants
to properly plot the pivot variant values.

src/lib/components/Graph.js

@@ -88,7 +88,7 @@ function expandParams(providedParams, location) {
       params.tooltipPt = categoryPointTooltip;
       params.yDomain = function() {return this.modelData.get('domains').get('ga');};
       params.xDomain = function() {
-        return ['', ...this.modelData.get('variants').filter(v => v !== this.modelData.get('pivot'))]
+        return ['', ...this.modelData.get('variants')]
       }
       params.dashedLines = [1.0]
       break;

src/lib/components/Legend.js

@@ -39,9 +39,6 @@ const useLegend = (d3Container, modelData, sizes, setLegendSwatchHovered, preset
     /* legend entries are arranged via the parent container's flexbox settings */
 
     let variants = modelData.get('variants')
-    if (preset==="growthAdvantage") {
-      variants = variants.filter((v) => v!==modelData.get('pivot'))
-    }
 
     const dom = d3.select(d3Container.current);
     dom.selectAll("*").remove();