Remove unnecessary assert_date_from_db

[kamipo]

assert_date_from_db was added at 6a2104d for SQL Server.
But latest sqlserver adapter work to pass expected behavior since
8e4624b.

[rails-bot]

r? @senny

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[sgrif]

@metaskills Can you confirm this is fine to merge?

[kamipo]

FYI: In sqlserver adapter 4.2, using SQLServer::Type::Date (inherits AcitveRecord::Type::Date) for deserializing date column value.

https://github.com/rails-sqlserver/activerecord-sqlserver-adapter/blob/v4.2.0/lib/active_record/connection_adapters/sqlserver_adapter.rb#L216-L217

        # Date and Time
        m.register_type              'date',              SQLServer::Type::Date.new

https://github.com/rails-sqlserver/activerecord-sqlserver-adapter/blob/v4.2.0/lib/active_record/connection_adapters/sqlserver/type/date.rb

module ActiveRecord
  module ConnectionAdapters
    module SQLServer
      module Type
        class Date < ActiveRecord::Type::Date

          # When FreeTDS/TinyTDS casts this data type natively.
          # include Castable

        end
      end
    end
  end
end

[metaskills]

Can you confirm this is fine to merge?

LGTM. I can pretty much cope with anything as needed later. FWIW, I just started the Rails 5 work yesterday. So I'll come back with issues as needed later.