Bump Python requirement imageio to 2.31.1

requirements.txt

 arkindex-export==0.1.3
 boto3==1.26.124
 editdistance==0.6.2
-imageio==2.26.1
+imageio==2.31.1
 numpy==1.24.3
 opencv-python==4.7.0.72
 PyYAML==6.0