[REG 4.9 -> 4.10] Wrong directory name for git clone

1. Select "File" -> "New File or Project..." -> " Import Project" -> "Git Clone" from the menu.
2. Paste "https://codereview.qt-project.org/qt-creator/qt-creator" as source repository.
   Creator will propose the directory name "-t-creator" for the clone.

Instead, the name of the repository "qt-creator" should be used as directory. This works correctly in Qt Creator 4.9.

Found by Squish test tst_git_clone.