Update dependency truffle to v5.4.15

Author: renovate-bot

package.json

@@ -62,6 +62,6 @@
     "mocha-lcov-reporter": "1.3.0",
     "prettier": "2.1.2",
     "solidity-coverage": "0.7.11",
-    "truffle": "5.1.48"
+    "truffle": "5.4.15"
   }
 }