Migration - custom entities not receiving field to configue

Problem/Motivation

From older version 1.4 to 3.x upgrade path we stumble on non-exist field in display type setting
Field was shown on article node but our custom one don't get it in administrative panel

Steps to reproduce

• Install old module
• Create custom type
• Upgrade module
• Check if field exist in display settings
• Check if admin/config/readmore_extrafield exist

Proposed resolution

Update uninstall/install process about custom fields
There isn't in admin/config/readmore_extrafield field

Proposed temporary fix

Remove type and add once more. This will flush configuration