x/crypto/ssh/agent: ecdsa key/cert typo

Introduced by me in 21536

Change-Id: I4a5f3507270a3d6eea9779508642ea5789d1efca
Reviewed-on: https://go-review.googlesource.com/24811
Reviewed-by: Han-Wen Nienhuys <hanwen@google.com>
Run-TryBot: Han-Wen Nienhuys <hanwen@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
2 files changed