targets: replace Bielefeld Jagdwerke with Bayerisches Flugzeugwerke (Augsburg)

BFW is the Messerschmitt factory (hence Bf109, commonly mislabelled Me109).
Bielefeld Jagdwerke was made-up and intended to (loosely) represent BFW.
As this is replacing one target with another, it doesn't break save-compat.