Switch Conda from `matplotlib` to `matplotlib-base`

[jakirkham]

Currently matplotlib is used in legate-boost's Conda requirements

legate-boost/dependencies.yaml

Line 170 in 590a830

- matplotlib>=3.9

However this pulls in GUI dependencies that are likely unneeded. To lighten the dependencies, would recommend using matplotlib-base with Conda instead

This can be done by adjusting matplotlib handling across dependency outputs