Add pyyaml dependency

This is necessary to correctly build gridtk.

Apologies for having this done is a separate merge request to the jinja2 one, I noticed this additional requirement too late.

bob/devtools/data/conda_build_config.yaml

@@ -419,6 +419,8 @@ pytorch:
   - 1.10.2  # [osx]
 pytorch_lightning:
   - 1.6.0
+pyyaml:
+  - 6.0
 pyzmq:
   - 22.3.0
 requests: