updated dev pip install in README.md

developer_docs/README.md

@@ -19,7 +19,7 @@ the Cromshell development environment can be set up by the following steps:
     python3 -mvenv venv
     . venv/bin/activate
     pip install --upgrade pip
-    pip install -e .[dev]
+    pip install -e . -r dev-requirements.txt
 ```
 
 After following the above development environment setup steps, cromshell should