internal/postgres: remove some error logging
internal/postgres: remove some error logging

We were logging some information to debug a deadlock, but it was
cluttering the logs and the messages had no context viewed in
isolation. Instead just log one row.

Change-Id: I0c7c261af0371f12edf51102a0b6ec20daf4bc9b
Reviewed-on: https://go-review.googlesource.com/c/pkgsite/+/348932
Trust: Jonathan Amsterdam <e3d3698b2ccd5955e4adf250d0785062d0f9018b@google.com>
Run-TryBot: Jonathan Amsterdam <e3d3698b2ccd5955e4adf250d0785062d0f9018b@google.com>
TryBot-Result: kokoro <2ac7b1f3fa578934c95181d4272be0d3bca00121@google.com>
Reviewed-by: Jamal Carvalho <e0195770807aa8c82b0b128d9c0423b5ad035172@golang.org>

golang/pkgsite,golang/pkgsite,golang/pkgsite,golang/pkgsite