Refine iFrame's Rubric type (#1766)

## Summary:
As part of the Server Side Scoring project, this refactors iFrame's Rubric type to show it is not needed for scoring. A TODO note is added to possibly remove this as part of LEMS-2440.

Issue: LEMS-2542

## Test plan:
- Confirm all checks pass

Author: Myranae

Reviewers: handeyeco

Required Reviewers:

Approved By: handeyeco

Checks: ✅ Publish npm snapshot (ubuntu-latest, 20.x), ✅ Lint, Typecheck, Format, and Test (ubuntu-latest, 20.x), ✅ Check builds for changes in size (ubuntu-latest, 20.x), ✅ Publish Storybook to Chromatic (ubuntu-latest, 20.x), ✅ Check for .changeset entries for all changed files (ubuntu-latest, 20.x), ✅ Cypress (ubuntu-latest, 20.x), ✅ gerald

Pull Request URL: #1766

.changeset/angry-foxes-cough.md

@@ -0,0 +1,5 @@
+---
+"@khanacademy/perseus": patch
+---
+
+Refine iFrame's Rubric type

packages/perseus/src/validation.types.ts

@@ -6,7 +6,6 @@ import type {
     PerseusGradedGroupWidgetOptions,
     PerseusGraphType,
     PerseusGroupWidgetOptions,
-    PerseusIFrameWidgetOptions,
     PerseusMatcherWidgetOptions,
     PerseusMatrixWidgetOptions,
     PerseusNumberLineWidgetOptions,
@@ -69,7 +68,8 @@ export type PerseusGrapherRubric = {
 
 export type PerseusGrapherUserInput = PerseusGrapherRubric["correct"];
 
-export type PerseusIFrameRubric = PerseusIFrameWidgetOptions;
+// TODO(LEMS-2440): Can possibly be removed during 2440; only userInput used
+export type PerseusIFrameRubric = Empty;
 
 export type PerseusIFrameUserInput = {
     status: UserInputStatus;

packages/perseus/src/widgets/iframe/iframe-validator.ts

@@ -1,23 +1,25 @@
 import type {PerseusScore} from "../../types";
 import type {PerseusIFrameUserInput} from "../../validation.types";
 
-export function iframeValidator(state: PerseusIFrameUserInput): PerseusScore {
+export function iframeValidator(
+    userInput: PerseusIFrameUserInput,
+): PerseusScore {
     // The iframe can tell us whether it's correct or incorrect,
     //  and pass an optional message
-    if (state.status === "correct") {
+    if (userInput.status === "correct") {
         return {
             type: "points",
             earned: 1,
             total: 1,
-            message: state.message || null,
+            message: userInput.message || null,
         };
     }
-    if (state.status === "incorrect") {
+    if (userInput.status === "incorrect") {
         return {
             type: "points",
             earned: 0,
             total: 1,
-            message: state.message || null,
+            message: userInput.message || null,
         };
     }
     return {