Fix for CMSSW 14_0_0 / ROOT 6.30 compilation

[nsmith-]

What I needed to do to compile in 14x

[guitargeek]

Already part of https://github.com/cms-analysis/HiggsAnalysis-CombinedLimit/pull/950.

Please, it would be nice to merge these small fixup PRs like the one I linked so people don't have to do duplicate work

[nsmith-]

Closing in favor of #950