chore: upgrade ganache-cli to 6.4.2 (#504)

Author: sohkai

package.json

@@ -37,7 +37,7 @@
     "eth-ens-namehash": "^2.0.8",
     "eth-gas-reporter": "^0.1.1",
     "ethereumjs-abi": "^0.6.5",
-    "ganache-cli": "6.2.3",
+    "ganache-cli": "^6.4.2",
     "mocha-lcov-reporter": "^1.3.0",
     "solidity-coverage": "0.5.8",
     "solium": "^1.2.3",