Remove unused graphviz import

This commit removes the unnecessary import of the graphviz module from glycosylate.py. The module was not used anywhere in the file, thus its removal cleans up the code and can potentially reduce dependencies.

package/src/sails/glycosylate.py

@@ -5,7 +5,6 @@
 import gemmi
 from pathlib import Path
 import json
-import graphviz
 import importlib.resources