Remove deprecated exports from the perseus package (#2164)

## Summary:
They have been moved to `perseus-core`.

Issue: none

Test plan:

CI should be green.

Author: benchristel

Reviewers: Myranae, jeremywiebe, handeyeco

Required Reviewers:

Approved By: Myranae, jeremywiebe

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

Pull Request URL: #2164

.changeset/poor-masks-return.md

@@ -0,0 +1,5 @@
+---
+"@khanacademy/perseus": major
+---
+
+Removes the following deprecated exports from `@khanacademy/perseus`: `parsePerseusItem`, `parseAndMigratePerseusItem`, `parseAndMigratePerseusArticle`, `isSuccess`, `isFailure`, `Result`, `Success`, `Failure`. Clients should import these from `@khanacademy/perseus-core` instead.

packages/perseus/src/index.ts

@@ -108,28 +108,6 @@ export {
     getAnswerFromUserInput,
     getImagesWithoutAltData,
 } from "./util/extract-perseus-data";
-export {
-    /**
-     * @deprecated - import this function from perseus-core instead
-     */
-    parsePerseusItem,
-    /**
-     * @deprecated - import this function from perseus-core instead
-     */
-    parseAndMigratePerseusItem,
-    /**
-     * @deprecated - import this function from perseus-core instead
-     */
-    parseAndMigratePerseusArticle,
-    /**
-     * @deprecated - import this function from perseus-core instead
-     */
-    isSuccess,
-    /**
-     * @deprecated - import this function from perseus-core instead
-     */
-    isFailure,
-} from "@khanacademy/perseus-core";
 
 export {
     generateTestPerseusItem,
@@ -203,20 +181,6 @@ export type {
     SharedRendererProps,
 } from "./types";
 export type {ParsedValue} from "./util";
-export type {
-    /**
-     * @deprecated - import this function from perseus-core instead
-     */
-    Result,
-    /**
-     * @deprecated - import this function from perseus-core instead
-     */
-    Success,
-    /**
-     * @deprecated - import this function from perseus-core instead
-     */
-    Failure,
-} from "@khanacademy/perseus-core";
 export type {Coord} from "./interactive2/types";
 export type {
     RendererPromptJSON,