Update root 6.12.x to get bug fix for std::unique_ptr

[gartung]

Need this patch for root to handle the case of reading back a unique_ptr from the root file
root-project/root@066167e

[cmsbuild]

A new Issue was created by @gartung Patrick Gartung.

@davidlange6, @Dr15Jones, @smuzaffar, @fabiocos, @kpedro88 can you please review it and eventually sign/assign? Thanks.

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[gartung]

Needed for cms-sw/cmssw#25239

[Dr15Jones]

@gartung CMSSW_10_4 is moving to ROOT 6.14. Could you check that the 6.14 we are already using in the ROOT_614 build contains the fix you need?

[gartung]

@Dr15Jones the branch cms/v6-14-00-patches/8e96679 does not have it yet. I think Phillipe submitted a backport request to root/v6-14-00-patches.

[gartung]

Backport PR is
root-project/root#2961

[gartung]

change to root/6-14-00-pathches