fix(package): update pg-promise to version 7.4.0 (#4514)

Author: greenkeeper[bot]

package.json

@@ -34,7 +34,7 @@
     "mongodb": "3.0.1",
     "multer": "1.3.0",
     "parse": "1.11.0",
-    "pg-promise": "7.3.3",
+    "pg-promise": "7.4.0",
     "redis": "2.8.0",
     "request": "2.83.0",
     "semver": "5.4.1",