Revert "Disable password auth on dib images"

This reverts commit 5d81e77e8c.

This breaks our images with:
"/etc/ssh/sshd_config line 85: Bad yes/no argument: No"

Change-Id: Id6feff2a6842764b2f375b77e33f52b5fc03944f

nodepool/elements/infra-package-needs/post-install.d/89-sshd

@@ -26,8 +26,3 @@ set -o pipefail
 # properly login.
 sed -i -e'/PermitRootLogin/d' /etc/ssh/sshd_config \
     && echo "PermitRootLogin Yes" >> /etc/ssh/sshd_config
-
-# NOTE(clarkb): Glean configures ssh keys only and not passwords. Disable
-# unnecessary password auth.
-sed -i -e '/PasswordAuthentication/d' /etc/ssh/sshd_config \
-    && echo "PasswordAuthentication No" >> /etc/ssh/sshd_config