Fix test errors with SMAC caused by dask 2021.07 (#1183)

* Fix test errors with SMAC caused by dask 2021.07

The latest version of dask (2021.07) does not play nicely with
`lazy_import` in SMAC.
Fixing the version to be `dask>=2021.06,<2021.07` fixes this.

* Removed lower bound for dask, reset distributed's lower bound

* Typo

Author: eddiebergman

requirements.txt

@@ -6,8 +6,8 @@ scipy>=0.14.1,<1.7.0
 joblib
 scikit-learn>=0.24.0,<0.25.0
 
-dask
-distributed>=2.2.0
+dask<2021.07
+distributed>=2.2.0,<2021.07
 pyyaml
 pandas>=1.0
 liac-arff