Fix RTD build

Set environment variable via the RTD dashboard. The previous approach wouldn't have worked, because package installation runs in a different environment,

Author: dweindl

.readthedocs.yaml

@@ -27,5 +27,3 @@ build:
       # Avoid setuptools-scm dirty Git index issues
       - git reset --hard HEAD
       - git clean -fdx
-      # Enforce fail_on_shallow for setuptools-scm
-      - export SETUPTOOLS_SCM_OVERRIDES_FOR_${READTHEDOCS_PROJECT//-/_}='{scm.git.pre_parse="fail_on_shallow"}'