build(deps): bump github.com/jackc/pgx/v4 from 4.13.0 to 4.15.0

Bumps [github.com/jackc/pgx/v4](https://github.com/jackc/pgx) from 4.13.0 to 4.15.0.
- [Release notes](https://github.com/jackc/pgx/releases)
- [Changelog](https://github.com/jackc/pgx/blob/master/CHANGELOG.md)
- [Commits](https://github.com/jackc/pgx/compare/v4.13.0...v4.15.0)

---
updated-dependencies:
- dependency-name: github.com/jackc/pgx/v4
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

go.mod

@@ -30,7 +30,7 @@ require (
 	github.com/gophercloud/gophercloud v0.22.0
 	github.com/hashicorp/go-retryablehttp v0.7.0
 	github.com/jackc/pgtype v1.10.0
-	github.com/jackc/pgx/v4 v4.13.0
+	github.com/jackc/pgx/v4 v4.15.0
 	github.com/julienschmidt/httprouter v1.3.0
 	github.com/kolo/xmlrpc v0.0.0-20201022064351-38db28db192b
 	github.com/labstack/echo/v4 v4.6.1