Bump truffle from 5.4.29 to 5.11.2 in /examples/truffle

Bumps [truffle](https://github.com/trufflesuite/truffle/tree/HEAD/packages/truffle) from 5.4.29 to 5.11.2.
- [Release notes](https://github.com/trufflesuite/truffle/releases)
- [Commits](https://github.com/trufflesuite/truffle/commits/truffle@5.11.2/packages/truffle)

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

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

examples/truffle/package.json

@@ -25,7 +25,7 @@
     "@gnosis.pm/util-contracts": "^3.0.1",
     "@openzeppelin/contracts": "^4.4.2",
     "@truffle/hdwallet-provider": "^2.0.0",
-    "truffle": "^5.4.29",
+    "truffle": "^5.11.2",
     "truffle-plugin-verify": "^0.5.20"
   }
 }