Pin documenteer==0.8.2.

This version claims to be compatible with Pydantic v2 and it works for
daf_butler, though there are reasons to doubt it's fully compatible.

.github/workflows/build_docs.yaml

@@ -31,7 +31,7 @@ jobs:
           pip install wheel
 
       - name: Install documenteer
-        run: pip install 'documenteer[pipelines]>=0.8'
+        run: pip install 'documenteer[pipelines]==0.8.2'
 
       - name: Install dependencies
         run: |