awslabs/tough is incompatible with new root-signing

[jku]

#1164 starts using "ecdsa" as the keytype as the specification now suggests.

This seems to break awslabs/tough: awslabs/tough#754
Failed to load repository: Failed to parse root metadata: Invalid SubjectPublicKeyInfo document at line 18 column 4

@kommendorkapten plans to disable the tough test for now: let's re-enable when possible

[haydentherapper]

This is now done.