Fix FTAG in the diff exclusion lists for frozen tier0

Prior to this MR we had the following in our diff exclusion list for frozen tier 0:

# Ignore most b-tagging outside the recommended taggers: DL1dv01 and GN2v01
xAOD::BTagging(?!.*PFlow.*DL1dv01_p.*)
xAOD::BTagging(?!.*PFlow.*GN2v01_p.*)

this was completely broken. My fault: I used an esoteric regex feature (negative lookahead assertions, see python docs) and then someone copied and pasted it. Breaking this down by line, this tells the regression tests to ignore variables in two cases:

• xAOD::BTagging(?!.*PFlow.*DL1dv01_p.*) matches anything that starts with BTagging and which is not DL1d
• xAOD::BTagging(?!.*PFlow.*GN2v01_p.*) matches anything that starts with BTagging and which is not GN2

Taken together, these two conditions match everything in the BTagging object. So we were disabling the frozen tier0 tests for b-tagging . The correct expression would have been xAOD::BTagging(?!.*PFlow.*(DL1dv01|GN2v01)_p.*).

But we're dropping DL1d soon anyway, so maybe we'll just keep it simple.

If this requires an update to the reference files we should probably try to merge it together with !78743 (merged).

Also tagging @robouque, @ligang, @dbaronmo (the FTAG SW conveners).