Bump @openzeppelin/test-helpers from 0.5.3 to 0.5.4 (#1999)

Bumps [@openzeppelin/test-helpers](https://github.com/OpenZeppelin/openzeppelin-test-helpers) from 0.5.3 to 0.5.4.
- [Release notes](https://github.com/OpenZeppelin/openzeppelin-test-helpers/releases)
- [Changelog](https://github.com/OpenZeppelin/openzeppelin-test-helpers/blob/master/CHANGELOG.md)
- [Commits](https://github.com/OpenZeppelin/openzeppelin-test-helpers/compare/v0.5.3...v0.5.4)

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

package.json

@@ -46,7 +46,7 @@
   "devDependencies": {
     "@openzeppelin/gsn-helpers": "^0.2.1",
     "@openzeppelin/gsn-provider": "^0.1.9",
-    "@openzeppelin/test-helpers": "^0.5.3",
+    "@openzeppelin/test-helpers": "^0.5.4",
     "chai": "^4.2.0",
     "concurrently": "^5.0.0",
     "eslint": "^6.5.1",