Revert "try 1.9.0 pin"

This reverts commit cd96c33.

Author: atravitz

environment.yaml

@@ -13,5 +13,5 @@ dependencies:
   - pytest-cov
   - pytest-xdist
   - python
-  - openfe==1.9.0
+  - openfe
   - openff-interchange-base != 0.5.1  # https://github.com/openforcefield/openff-interchange/issues/1450