build: update pangolin environment

Bumps version and adds nodefaults channel. Bounding setuptools avoids ModuleNotFoundError when pangolin tries to import pkg_resources (deprecated, see https://setuptools.pypa.io/en/latest/pkg_resources.html and cov-lineages/pangolin#570).

Author: ahmig

workflow/envs/pangolin.yaml

@@ -1,5 +1,7 @@
 channels:
   - conda-forge
   - bioconda
+  - nodefaults
 dependencies:
-  - pangolin==4.3.1
+  - pangolin==4.3.4
+  - setuptools<81