Change wording of import warning for PyQt/Qt versions 5.11 and 5.12

Two separate pull requests indicate an issue translating the warning
for when an import is attempted with PyQt/Qt versions 5.11 and 5.12.
As such change the warning message.

See PRs #668 and #701.

manuskript/mainWindow.py

@@ -1596,7 +1596,7 @@ def doImport(self):
             print("WARNING:", warning1, warning2)
 
             msg = QMessageBox(QMessageBox.Warning,
-                self.tr("Proceeding might crash and lose data"),
+                self.tr("Proceed with import at your own risk"),
                 "<p><b>" +
                     warning1 +
                 "</b></p>" +