Update Test CI (pymc-devs#474)

* update ci and simplify test env

* Remove default channel when setting up ci env

* Cancel test runs on PRs if another commit comes in

* revert some changes, pin libgcc<15

* use correct shell name

Author: jessegrabowski

conda-envs/environment-test.yml

@@ -3,18 +3,16 @@ channels:
 - conda-forge
 - nodefaults
 dependencies:
-  - pymc>=5.24.1
-  - pytensor>=2.31.4
+  - pymc>=5.21.1
   - scikit-learn
-  - better-optimize>=0.1.5
+  - better-optimize
   - dask<2025.1.1
   - xhistogram
   - statsmodels
   - numba
   - pytest
   - pytest-cov
-  - pydantic>=2.0.0
-  - preliz>=0.20.0
+  - libgcc<15
   - pip
   - pip:
       - jax