Revert "Temporarily install pymc via pip"

This reverts commit f31c518.

Author: ricardoV94

conda-envs/environment-test.yml

@@ -4,10 +4,10 @@ channels:
 - defaults
 dependencies:
 - pip
+- pymc>=5.1.2
 - pytest-cov>=2.5
 - pytest>=3.0
 - dask
 - xhistogram
 - pip:
-  - pymc>=5.1.2  # CI was failing to resolve
   - blackjax

conda-envs/windows-environment-test.yml

@@ -4,9 +4,8 @@ channels:
 - defaults
 dependencies:
 - pip
+- pymc>=5.1.2
 - pytest-cov>=2.5
 - pytest>=3.0
 - dask
 - xhistogram
-- pip:
-  - pymc>=5.1.2  # CI was failing to resolve