If you're using sha1 0.6 you're now pulling in sha1_smol 1.0.0. This is because the crate was renamed. Under the old name "sha1" in the future "sha-1" will be published which is the SHA1 implementation by RustCrypto.
These days a lot of the ecosystem is moving over to RustCrypto and it is sensible for this to be the default implementation. sha1_smol will stay around for if you need a zero dependency SHA1 implementation.
For discussions use this issue: #42