Remove deprecation warning for ActiveModel::Errors#keys

Ref: #339739 (closed)

What does this MR do and why?

This MR removes deprecation warning for ActiveModel::Errors#keys required for rails 7.

Screenshots or screen recordings

pages_domain.errors.keys
DEPRECATION WARNING: ActiveModel::Errors#keys is deprecated and will be removed in Rails 6.2.

To achieve the same use:

  errors.attribute_names (called from block (5 levels) in <top (required)> at (pry):1)
=> [:certificate, :key]

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