Include pocl_dev conda label channel for CI

Author: inducer

.test-conda-env-py3.yml

@@ -1,5 +1,8 @@
 name: test-conda-env
 channels:
+# For https://github.com/pocl/pocl/pull/1069
+# See https://github.com/conda-forge/pocl-feedstock/pull/80
+- conda-forge/label/pocl_dev
 - conda-forge
 - nodefaults