Update dependency @testing-library/react to v15

Author: renovate[bot]

package.json

@@ -38,7 +38,7 @@
   "homepage": "https://github.com/mitodl/course-search-utils#readme",
   "dependencies": {
     "@mitodl/open-api-axios": "^2024.5.6",
-    "@testing-library/react": "12",
+    "@testing-library/react": "15",
     "@testing-library/user-event": "^14.5.2",
     "axios": "^1.6.7",
     "fuse.js": "^7.0.0",