Remove superfluous QTextStream::setCodec call
QTextStream::setCodec doesn't do anything beyond updating the internal codec pointer, and save/restore the seek position if there already is a read buffer (which isn't the case here). Given our very next call is setCodec() again, this call has no effect.
In itself this doesn't make much of a difference, but it helps with reasoning about this code, which needs to be changed significantly for Qt6.