chore(deps-dev): bump tsdown in /packages/test-suite

Bumps [tsdown](https://github.com/rolldown/tsdown) from 0.11.13 to 0.20.1.
- [Release notes](https://github.com/rolldown/tsdown/releases)
- [Commits](rolldown/tsdown@v0.11.13...v0.20.1)

---
updated-dependencies:
- dependency-name: tsdown
  dependency-version: 0.20.1
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

packages/test-suite/package.json

@@ -55,7 +55,7 @@
   },
   "devDependencies": {
     "dotenv-cli": "^11.0.0",
-    "tsdown": "^0.11.9",
+    "tsdown": "^0.20.1",
     "typescript": "^5.8.3",
     "vitest": "^3.1.3"
   },