BdsToVVand4H_run3_checks -- fix wrong polarity on MC

Production !1341 (merged) added data and MC for MagUp, however I realised that the MC samples still had the MagDown BK query instead of changing to MagUp...

I have archived all of the MC samples from the above mentioned production and this production is exactly the same but just containing the MC samples again but now with the correct BK query (the data samples in the previous production are fine so I left those running). Apologies for the mistake!