Remove "ced" dependency

[FlyingDR]

ced usage was removed by d3a8b46, but it is still listed as a package dependency:

haraka-plugin-mongodb/package.json

Line 34 in b2b8668

"ced": "^2.0.0",

it would be good to remove it because it have own binary dependency which may require native binary build process during npm install without any practical purpose.