Set default `is_FT=False`

[ShantanuKodgirwar]

@dboonz

@larsloetgering and I had an issue in our project that arose because of this setting here:

https://github.com/PtyLab/PtyLab.py/blob/889bf8fdcc3789e264d955a30b7972ce04953a65/PtyLab/Operators/Operators.py#LL571C59-L571C59

It also deviates from Ptylab.m and it's probably a good idea to set is_FT=False as the default option.