Returned a clone of the element symbol params instead of the original const, removing a todo comment

src/mol-theme/color/element-symbol.ts

@@ -46,7 +46,7 @@ export const ElementSymbolColorThemeParams = {
 };
 export type ElementSymbolColorThemeParams = typeof ElementSymbolColorThemeParams
 export function getElementSymbolColorThemeParams(ctx: ThemeDataContext) {
-    return ElementSymbolColorThemeParams; // TODO return copy
+    return PD.clone(ElementSymbolColorThemeParams)
 }
 
 export function elementSymbolColor(colorMap: ElementSymbolColors, element: ElementSymbol): Color {