fix: Invalid case on writeconcern makes skip check fail

[unusualbob]

Description

When deprecating top-level writeConcern keys, some code was added to specifically skip them in createUnifiedOptions. You can see the change here

This was ok for all keys except writeConcern, as the key being checked is cast to lowercase, but the original value is not. If given an input key of writeConcern it is converted to writeconcern and then always compared against writeConcern causing the check to always be false. This means that if you have connection options of:

writeConcern: {
  w: 1
}

the createUnifiedOptions function will ultimately add w:1 to the final options object and result in deprecation errors being thrown, despite a valid config.

It seems the values in skip are not used anywhere else, so the simplest solution was to change the case of the value in the skip array.

[nbbeeken]

Thanks for catching this and submitting a fix! LGTM 🚀