TST: correct parquet test expected partition column dtype for pyarrow 2.0
Follow-up on https://github.com/pandas-dev/pandas/pull/35814, but now incorporating the changes in pyarrow 2.0

cc @alimcmaster1 

Also related to https://github.com/pandas-dev/pandas/issues/37286 and https://github.com/pandas-dev/pandas/pull/37296/ (timezone related failures), but doing this fix separate as it's not something that needs to be reverted.

the travis-36-cov builds regularly fails to build with `The build has been terminated` on 1.1.x so haven't yet seen this failing on 1.1.x but probably makes sense to backport this. thanks @jorisvandenbossche  > the travis-36-cov builds regularly fails to build with `The build has been terminated` on 1.1.x so haven't yet seen this failing on 1.1.x but probably makes sense to backport this.

yeah this is happening regularly, odd @meeseeksdev backport 1.1.x > > the travis-36-cov builds regularly fails to build with `The build has been terminated` on 1.1.x so haven't yet seen this failing on 1.1.x but probably makes sense to backport this.
> 
> yeah this is happening regularly, odd

i'll open a dedicated issue so that references to this can be collated. 