DOC: remove okwarning once pyarrow 0.12 is released

[jorisvandenbossche]

TODO: Revert #24591 once pyarrow is released

[jbrockmendel]

Do we have a minimal pyarrow we support? environment.yml lists pyarrow>=0.7.0. There are some special cases in internals.blocks for pyarrow compat that would be nice to get rid of eventually.

[jreback]

not averse to bumping

[jbrockmendel]

It looks like the commit that removed pyarrow's deprecated usage was 2018-01-25 apache/arrow@6bb1d1b. The first release after that looks like 0.9.0 on 2018-03-16

[jreback]

bump to 0.9.0 would be fine

[jorisvandenbossche]

I am also fine with bumping to 0.9.0.
That is however unrelated to the original issue here, though. @jbrockmendel can you open a new issue for that?