time wrongly displayed in zh_TW locale

Qt.Locale.ShortFromat is set to be default to displayed in 24 hour format in zh_TW.UTF-8 locale, but it is somehow prefixed with a "B"

steps:

1. open qtcreator
2. create tutorial project from /usr/share/doc/qt6/examples/tutorials/alarms
3. go to the build directory
4. run it with LC_ALL=zh_TW.UTF-8 ./alarm method and check that there is the "B" prefix.

Additional information:

• It is originally found as in Plasma6's lockscreen as well as the SDDM display manager greeter with Breeze theme.
• It is also confirmed on a fresh-installed opensuse Tumbleweed system, which defaults to plasma6+qt6.
• this is not the minimum proof of concept, but it does show the bug.