feat: venom has fixed a problem with casing preserving

[Ivan Velasco]

As of ovh/venom#709 a fix was provided to preserve casing. This affects this plugin as we lower case when converting json payload to result.bodyjson

e.g.

{
   "data": {
    "firstName": "firstName"
}

gets converted to

- result.bodyjson.data.firstname ShouldEqual "firstName"

update required to keep casing and produce

- result.bodyjson.data.firstName ShouldEqual "firstName"