datahub: Bump matplotlib *slightly*
datahub: Bump matplotlib *slightly*

The datascience package isn't compatible with 3.3 yet,
but 3.1.3 has python 3.8 wheels

ryanlovett/datahub,berkeley-dsep-infra/datahub,berkeley-dsep-infra/datahub,ryanlovett/datahub,ryanlovett/datahub,berkeley-dsep-infra/datahub