[SR][SR Tree] Show the descriptions again (#2096)

## Summary:
By changing the text getting to `innerText` insted of
`textContent`, we actually stopped displaying the
descriptions.

Go back to using `textContent` so the descriptions
display again.

Issue: none

## Test plan:
Storybook
- http://localhost:6006/?path=/story/perseuseditor-widgets-interactive-graph--interactive-graph-linear
- check that the screen reader tree shows all the
  linear graph descriptions

| Before | After |
| --- | --- |
| ![Screenshot 2025-01-13 at 10 12 52 AM](https://github.com/user-attachments/assets/5d6f9ce7-f692-4225-bb94-e748db867f2e) | ![Screenshot 2025-01-13 at 10 16 24 AM](https://github.com/user-attachments/assets/80528e07-84fb-4262-bcfb-936f21deb501) |

Author: nishasy

Reviewers: benchristel

Required Reviewers:

Approved By: benchristel

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

Pull Request URL: #2096

.changeset/cool-shrimps-grin.md

@@ -0,0 +1,5 @@
+---
+"@khanacademy/perseus-editor": patch
+---
+
+[SR][sr tree] Show descriptions again

packages/perseus-editor/src/widgets/interactive-graph-editor/components/interactive-graph-sr-tree.tsx

@@ -55,7 +55,7 @@ export function getAccessibilityAttributes(
             const descriptions = ariaDescribedby.split(/ +/);
             for (const description of descriptions) {
                 const descriptionString =
-                    document.getElementById(description)?.innerText;
+                    document.getElementById(description)?.textContent;
 
                 if (descriptionString) {
                     elementAttributes.push({