remove() doesn't support reserved words

[fr3shn3ss]

when using remove('TTL') or remove('year') the update expression doesn't handle it.

UpdateExpression =============> "SET test = :a, age = :b REMOVE year"

AWS Exception
ValidationException: Invalid UpdateExpression: Attribute name is a reserved keyword; reserved keyword: year

[kayomarz]

@fr3shn3ss Thank you for reporting this.

I have fixed this and published version 4.0.1 Please can you give it a try.
Thank you.