Fix reviewers for dependabot - 'assignees' is only for individuals (#…

…1935)

## Summary:

*sigh* I can't read. 

`assignees` => https://docs.github.com/en/code-security/dependabot/dependabot-version-updates/configuration-options-for-the-dependabot.yml-file#assignees

> Use assignees to specify individual assignees for all pull requests raised for a package manager.

`reviewers` ==> https://docs.github.com/en/code-security/dependabot/dependabot-version-updates/configuration-options-for-the-dependabot.yml-file#reviewers

> Use reviewers to specify individual reviewers or teams of reviewers for all pull requests raised for a package manager. You must use the full team name, including the organization, as if you were @mentioning the team.

Issue: "none"

## Test plan:

Author: jeremywiebe

Reviewers: jandrade, jeremywiebe, mark-fitzgerald

Required Reviewers:

Approved By: mark-fitzgerald

Checks: ✅ Publish npm snapshot (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), ✅ Cypress (ubuntu-latest, 20.x), ✅ Check builds for changes in size (ubuntu-latest, 20.x), ✅ Publish Storybook to Chromatic (ubuntu-latest, 20.x), ✅ gerald, ✅ .github/dependabot.yml

Pull Request URL: #1935

.github/dependabot.yml

@@ -12,8 +12,9 @@ updates:
           - dependency-name: "@khanacademy/eslint-plugin"
           - dependency-name: "@khanacademy/wonder-blocks-*"
           - dependency-name: "@khanacademy/wonder-stuff-*"
-      assignees:
-          - "@Khan/perseus"
+      reviewers:
+          - "Khan/perseus"
+          - "Khan/wonder-blocks"
 
       # Grouped updates for Wonder Blocks and Wonder Stuff releases.
       # This helps us to stay in sync with the latest releases of these packages.