cmd/pkgsite: remove dcensus
cmd/pkgsite: remove dcensus

Since the fetch code no longer records metrics, the pkgsite command
doesn't need to talk to OpenCensus.

For golang/go#48010

Change-Id: I2793046725cd8c66ddfb585370ba2bf4890a9366
Reviewed-on: https://go-review.googlesource.com/c/pkgsite/+/346810
Trust: Jonathan Amsterdam <e3d3698b2ccd5955e4adf250d0785062d0f9018b@google.com>
Run-TryBot: Jonathan Amsterdam <e3d3698b2ccd5955e4adf250d0785062d0f9018b@google.com>
Reviewed-by: Julie Qiu <8d32267b6b4884cf35adeaccde2b6857ae11aace@golang.org>

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