fix(file): revert ok button behaviour for open dialogs

[Dorosty]

I made a mistake in #21 and I now realize what the previous code was intended for. In our testing, the open-file dialog now has its OK button disabled by default when selecting directories, even when an initial path is given.

I believe the correct behaviour for the OK button should be:

Dialog type (this.args.type)	File Type (this.args.filetype)	is File Name Provided (!!this.args.filename)	is OK button enabled as a result
open	file	no	no
open	file	yes	yes
open	directory	no	yes (used to be no)***
open	directory	yes	yes***
open	file	no	no
open	file	yes	yes
open	directory	no	no
open	directory	yes	yes

*** only path will get used for the final value since there is no input box for directory name

We have tested this extensively and hope that it works as intended now. Apologies!

Also, pleas note that the expression can be further abbreviated to:

buttons: {
  ok: (this.args.type === 'open' && this.args.filetype === 'directory') || !!this.args.filename
}

[andersevenrud]

No worries :)

Released.