Add a newline after password input

[knqyf263]

Summary

There is no newline after entering a password and the output is hard to read.

Before:

$ cosign sign --key cosign.key knqyf263/cosign-test
an error occurred: no provider found for that key reference, will try to load key from disk...
Enter password for private key: Pushing signature to: index.docker.io/knqyf263/cosign-test

After:

$ cosign sign --key cosign.key knqyf263/cosign-test
an error occurred: no provider found for that key reference, will try to load key from disk...
Enter password for private key:
Pushing signature to: index.docker.io/knqyf263/cosign-test

Release Note

Add a newline after entering password