Update docs/sandbox.md

Author: amotl

docs/sandbox.md

@@ -55,7 +55,7 @@ role-implementations, see [`gridtable.py`], [`infocard.py`], and [`tag.py`].
 
 ```shell
 # Install a few more prerequisites.
-pip install --editable ".[release]"
+pip install --editable '.[release]'
 
 # Designate a new version.
 git tag v0.1.0