fix(package): update pg to version 7.4.3

Author: greenkeeper[bot]

package.json

@@ -14,7 +14,7 @@
     "base-64": "^0.1.0",
     "debug": "^3.1.0",
     "express": "^4.16.2",
-    "pg": "^6.4.2",
+    "pg": "^7.4.3",
     "pg-hstore": "^2.3.2",
     "sequelize": "^4.22.6"
   },