It's actually still there - see https://github.com/arrbee/libgit2/blob/fix-1695/src/transports/cred.c#L91

Diff is just being dumb and taking the `memset` that used to be in `ssh_keyfile_passphrase_free` and considering it part of this function.

I don't think a memzero is needed for the publickey part of the credential, but I'd be happy to change it if you think we should.