remove references to environment.yml

Author: afeld

meta/instructor_guide.md

@@ -4,7 +4,7 @@ _While this is meant as internal documentation for the instructor, others are we
 
 ## Adding/updating packages
 
-1. Modify [`environment.yml`](https://github.com/afeld/python-public-policy/blob/main/extras/environment.yml)
+1. Modify [`requirements.txt`](https://github.com/afeld/python-public-policy/blob/main/requirements.txt)
 1. Run
 
    ```sh

requirements.txt

@@ -40,7 +40,6 @@ nbconvert>=7.16.6
 nbdime
 pytest
 
-# this needs to stay in sync with docs/environment.yml
-jupyter-book==1.0.4.post1
+jupyter-book==1.*
 # https://github.com/sphinx-doc/sphinx/issues/10440#issuecomment-1556180835
 sphinx>=6.2.0