Fields property in `objs_user_profile` has incorrect type

[vmasek]

Description

Type of one of the objs_user_profile properties is incorrect. property fields has a type which is an array ("type": ["object", "null", "array"]) which is incorrect according to OpenAPI 2.0 docs, where type can be only a string

It is similar to https://github.com/slackapi/slack-api-specs/issues/8

What type of issue is this? (place an x in one of the [ ])

• [x] bug
• [ ] enhancement (feature request)
• [ ] question
• [ ] documentation related
• [ ] testing related
• [ ] discussion

Requirements (place an x in each of the [ ])

• [x] I've read and understood the Contributing guidelines and have done my best effort to follow them.
• [x] I've read and agree to the Code of Conduct.
• [x] I've searched for any related issues and avoided creating a duplicate issue.

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