Revert "fix file open dialog default directory for kwrite as well"

This reverts commit 86b83aa2.
This reverts commit 3b684d26.

The issue has been fixed in frameworksintegration, what we did
before is actually correct. To cite documentation of
QFileDialog::getOpenFileName:

"The file dialog's working directory will be set to dir. If dir includes
a file name, the file will be selected."

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