[Python][Packaging] Remove numpy required dependency from conda-forge packaging for PyArrow

[amoeba]

Describe the enhancement requested

In #43846 we removed numpy as a required dependency from PyArrow but this change only removed the dependency from our packages on PyPi and not on conda-forge. We should probably continue the effort and remove numpy as a required dependency on conda-forge.

I was able to confirm this locally, not that numpy is included:

❯ conda install --dry-run -c conda-forge pyarrow==18.0.0
...>%...
The following packages will be downloaded:

    package                    |            build
    ---------------------------|-----------------
    aws-crt-cpp-0.29.0         |       h871d450_6         224 KB  conda-forge
    aws-sdk-cpp-1.11.407       |       h19709bb_6         2.6 MB  conda-forge
    libarrow-18.0.0            |   h6fea68a_0_cpu         5.2 MB  conda-forge
    libarrow-acero-18.0.0      |   h286801f_0_cpu         480 KB  conda-forge
    libarrow-dataset-18.0.0    |   h286801f_0_cpu         486 KB  conda-forge
    libarrow-substrait-18.0.0  |   hdcc9e87_0_cpu         447 KB  conda-forge
    libparquet-18.0.0          |   hda0ea68_0_cpu         861 KB  conda-forge
    numpy-2.1.3                |  py312h94ee1e1_0         6.1 MB  conda-forge
    pyarrow-18.0.0             |  py312ha814d7c_0          25 KB  conda-forge
    pyarrow-core-18.0.0        |py312hc40f475_0_cpu         3.7 MB  conda-forge
    ------------------------------------------------------------
                                           Total:        20.1 MB

Component(s)

Packaging, Python