Disable broken and redundant CKKWL acceptance correction in common JO

Andy Buckley requested to merge abuckley/athena:21.6 into 21.6

Code at the bottom of the CKKWL common JO fragment attempted to use acmake to obtain the Pythia8 native version, but didn't work. The result was that it always applied a manual acceptance correction, although that was only required for versions < 8.219. This caused significantly wrong cross-sections to be written into the ATLAS metadata.

We don't need the workaround any more and I can't see that we'll ever need it in the releases built from git. At the moment I've commented it out with an explanation, but maybe better that I clean up properly by deleting it.

Fixes ATLMCPROD-8537

@ewelina It would be good if we can get this disabling in place before making the currently requested release with Py 8.3.

Edited by Giancarlo Panizzo

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