Doc: Include note on "channel_priority strict" in description

[klieret]

Solution to issue cannot be found in the documentation.

• I checked the documentation.

Issue

I lost quite some time trying to install ROOT based on the instructions from https://anaconda.org/conda-forge/root/ before I found the hint about

conda config --set channel_priority strict
conda create -c conda-forge --name <my-environment> root

at https://root.cern/install/#conda.

This should be included on https://anaconda.org/conda-forge/root/ as well.

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Including the errors I got previously to help search engines find this (all solved now):

Fatal in <TROOT::InitInterpreter>: cannot load library /scratch/gpfs/kl5675/miniconda3/envs/madgraph/lib/libstdc++.so.6: version `GLIBCXX_3.4.30' not found (required by /scratch/gpfs/kl5675/miniconda3/envs/madgraph/lib/libRIO.so)