ci: use matching openssl key digest

.circleci/config.yml

@@ -200,8 +200,11 @@ jobs:
       - attach_workspace: *attach_options
       - run:
           name: Decrypt Credentials
+          # Note: when changing the image, you might have to re-encrypt the credentials with a 
+          # matching version of openssl.
+          # See https://stackoverflow.com/a/43847627/2116927 for more info.
           command: |
-            openssl aes-256-cbc -d -in .circleci/github_token -k "${KEY}" -out ~/github_token
+            openssl aes-256-cbc -d -in .circleci/github_token -k "${KEY}" -out ~/github_token -md md5
       - run:
           name: Deployment to Snapshot
           command: |