Update ProxiedFuture.ts (updated doc comment)

Author: liamgriffiths

src/ProxiedFuture.ts

@@ -32,7 +32,7 @@ export const makeProxyFactory = (futureTable: FutureTable = {}) => {
         if (prop === GET_TARGET) return target;
 
         if (prop === Symbol.toPrimitive) {
-          // When the prop is not a primitive (number, string, Symbol) it will be attempted
+          // When the prop is not a `string` or `Symbol` it will be attempted
           // to be converted into one. This case will happen when the prop is a Future.
           //
           // Because only primitive types can be used as property accessors, what we're doing