ENH: Remove reference to arrow-cpp from the README

[raulcd]

Comment:

The readme still refers to arrow-cpp and we should probably remove that reference to avoid confusion.

[h-vetinari]

It only refers to arrow-cpp as the name of the feedstock, which we cannot change without recreating an entirely new feedstock -- and then losing a lot of history, not just in terms of commits (which could be force-pushed), but also discussions in issues/PR etc.

It's not realistic to change unfortunately (we cannot do a manual rename as the feedstock names are plugging into so many places in the bot infrastructure that this would just cause horrific breakage)

The silver lining is that arrow-cpp appears nowhere in the list of installable packages:

mamba install apache-arrow-proc libarrow libarrow-acero libarrow-all libarrow-dataset libarrow-flight libarrow-flight-sql libarrow-gandiva libarrow-substrait libparquet