run `go fmt` on widgets

[ilius]

widgets.go is not compatible with go fmt, which makes it hard to work on this code. You have to disable formatting on your editor and are not able to run go fmt manually either.

I tried running go generate but failed:

stringer: no values defined for type QDialogButtonBox__ButtonLayout
widgets.go:11107: running "stringer": exit status 1

There are more errors if I disable this one.

[CLAassistant]

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