Pin to mdtraj != 1.11

The bug seems to already be fixed on main, but the fix isn't in a
release yet. This should give a temporary fix.

Author: dwhswenson

binder/environment.yml

@@ -12,5 +12,5 @@ dependencies:
   - openpathsampling-cli
   - openmmtools
   - jupyterlab
-  #- ipywidgets <8
+  - mdtraj != 1.11  # formal charge error round-tripping Topology via pandas
 prefix: /Users/dwhs/miniconda3/envs/ops-tutorial