Fix unit tests for ktimecombobox

Since Qt 6.8, QLocale().timeFormat() returns always Ap so the previous code would always try to convert the local specific AM/PM specifier to upposer case e.g. "π.μ." "μ.μ." to "Π.Μ." "Μ.Μ." wich would not match the example anymore and then it would not be converted to the 'x' mask character and prevent the user to set a time with "π.μ." and only with "μ.μ." converting the date from midnight to noon.