Update oras/auth/ecr.py

Co-authored-by: Vanessasaurus <814322+vsoch@users.noreply.github.com>
Signed-off-by: Matteo Mortari <matteo.mortari@gmail.com>

Author: tarilabs

oras/auth/ecr.py

@@ -4,7 +4,6 @@
 
 import re
 
-# do not `import boto3` as it's the `ecr` extra, see setup.py
 import requests
 
 import oras.auth.utils as auth_utils