Correct stale documentation section about SSH authentication

We no longer rely on the tuple (username, key) to be unique, but instead
just force the username to be unique.  Thus this entire section of the
documentation is now factually wrong, and should be removed.

Change-Id: Ibd5b860e214096fff4769962321b38a6279e7547
Signed-off-by: Shawn O. Pearce <sop@google.com>
1 file changed