Fix var name in conda_build_config.yaml

pytest-cov -> pytest_cov in conda_build_config.yaml.

bob/devtools/data/conda_build_config.yaml

@@ -178,7 +178,7 @@ pyqtgraph:
   - 0.11.0
 pytest:
   - 6.1.1
-pytest-cov:
+pytest_cov:
   - 2.10.1
 python_graphviz:
   - 0.14.2