fix: github.com/jackc/pgx go.mod

[rickif]

This project gets error as below when we run go mod tidy, which led by the wrong import version of github.com/jackc/pgx.

go: finding module for package github.com/jackc/pgx/pgxpool
github.com/influxdata/influxdb-comparisons/cmd/bulk_load_timescale imports
        github.com/jackc/pgx/pgxpool: module github.com/jackc/pgx@latest found (v3.6.2+incompatible), but does not contain 

This PR is to solve this problem.