removeAdditional is not consistent with documentation.

**What version of Ajv are you using? Does the issue happen if you use the latest version?**

7.0.3

**Ajv options object**

```javascript
{ removeAdditional: true }
```

**JSON Schema**

```javascript
{
type: "object",
oneOf: [
{
properties: {
foo: { type: "string" }
},
required: ["foo"],
additionalProperties: false
},
{
properties: {
bar: { type: "integer" }
},
required: ["bar"],
additionalProperties: false
}
]
}
```

**Sample data**

```javascript
{ bar: 1 }
```

**Your code**

Please see this codesanbox. Change ajv version from 7 to 6 to compare.

https://codesandbox.io/s/ajv6-oneof-removeadditional-sf9yt?file=/src/App.tsx

**Validation result, data AFTER validation, error messages**

The data is valid.

**What results did you expect?**

According to the doc "With the option `removeAdditional: true` the validation will pass for the object `{ "foo": "abc"}` but will fail for the object `{"bar": 1}`. It happens because while the first subschema in `oneOf` is validated, the property `bar` is removed because it is an additional property according to the standard (because it is not included in `properties` keyword in the same schema)."

This was true in ajv 6 but not in ajv 7.

As far as I'm concerned, I believe that that the example in the doc is pretty odd and that the current behavior is correct.

**Are you going to resolve the issue?**

No, I am working on the removeUnevaluated property and I believe that removeAdditional has many counterintuitive elements and should be deprecated.