Bump minimum version requirements for dask from 2.15 to 2.24

[Illviljan]

Dask released 2.24 around august 22 2020: https://github.com/dask/dask/releases/tag/2.24.0

• May help fixing errors in Rely on NEP-18 to dispatch to dask in duck_array_ops #5571
• Passes pre-commit run --all-files
• User visible changes (including notable bug fixes) are documented in whats-new.rst

[github-actions]

Unit Test Results

         6 files  ±0           6 suites  ±0   49m 30s ⏱️ ±0s
16 225 tests ±0  14 489 ✔️ ±0  1 736 💤 ±0  0 ❌ ±0 
90 546 runs  ±0  82 363 ✔️ ±0  8 183 💤 ±0  0 ❌ ±0 

Results for commit 4fd81b5. ± Comparison against base commit 4fd81b5.

♻️ This comment has been updated with latest results.

[max-sixty]

This looks good!

@keewis is this compatible / duplicative with your min versions check script?

[keewis]

No, but it will be in 2-3 days (we're using the dates on conda-forge instead of the official release dates):

 dask              2.24    (2020-08-24) 2.23    (2020-08-14) > (!)
 distributed       2.24    (2020-08-22) 2.23    (2020-08-14) > (!)

I guess we should probably wait with the merge until then to avoid causing the CI to break. Then again, other CI are already failing so it might not make a difference.

[Illviljan]

Yeah, a little unfortunate that dask had a later date on conda-forge. But I wasn't expecting an immediate merge anyway.

[Illviljan]

The minimum version check now passes for both dask and distributed. This is ready for review/merge now.

[dcherian]

Thanks @Illviljan

[keewis]

thanks, @Illviljan