docs(mongoose): removed duplicated line

[lpizzinidev]

The line explaining the debug option is already specified above:

mongoose/lib/index.js

Line 204 in c77dd1b

* - 'debug': If `true`, prints the operations mongoose sends to MongoDB to the console. If a writable stream is passed, it will log to that stream, without colorization. If a callback function is passed, it will receive the collection name, the method name, then all arguments passed to the method. For example, if you wanted to replicate the default logging, you could output from the callback `Mongoose: ${collectionName}.${methodName}(${methodArgs.join(', ')})`.

[vkarpov15]

Thanks 👍