Bump Python requirement fontTools to 4.39.3

requirements.txt

 arkindex-export==0.1.2
 boto3==1.26.124
 editdistance==0.6.2
-fontTools==4.39.2
+fontTools==4.39.3
 imageio==2.26.1
 mlflow-skinny==2.2.2
 networkx==3.1