prometheus: bump prom/prometheus, prom/alertmanager
Created by: bobheadxi
The config library was bumped in https://github.com/sourcegraph/sourcegraph/commit/d3ade214bd19dfcc868fd864ccfe5db7c0dcc428#diff-33ef32bf6c23acb95f5902d7097b7a1d5128ca061167ec0716715b0b9eeaa5f6L117 without a corresponding bump in Prometheus, causing breakage in prod: https://sourcegraph.slack.com/archives/CMBA8F926/p1649953415685099