Bump github.com/prometheus/client_model from 0.5.0 to 0.6.0 (#1010)

Bumps [github.com/prometheus/client_model](https://github.com/prometheus/client_model) from 0.5.0 to 0.6.0.
- [Release notes](https://github.com/prometheus/client_model/releases)
- [Commits](https://github.com/prometheus/client_model/compare/v0.5.0...v0.6.0)

---
updated-dependencies:
- dependency-name: github.com/prometheus/client_model
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

go.mod

@@ -9,7 +9,7 @@ require (
 	github.com/go-kit/log v0.2.1
 	github.com/lib/pq v1.10.9
 	github.com/prometheus/client_golang v1.19.0
-	github.com/prometheus/client_model v0.5.0
+	github.com/prometheus/client_model v0.6.0
 	github.com/prometheus/common v0.48.0
 	github.com/prometheus/exporter-toolkit v0.10.0
 	github.com/smartystreets/goconvey v1.8.1