build(deps): bump github.com/prometheus/client_golang

Bumps [github.com/prometheus/client_golang](https://github.com/prometheus/client_golang) from 1.17.0 to 1.18.0.
- [Release notes](https://github.com/prometheus/client_golang/releases)
- [Changelog](https://github.com/prometheus/client_golang/blob/main/CHANGELOG.md)
- [Commits](https://github.com/prometheus/client_golang/compare/v1.17.0...v1.18.0)

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

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

vendor/github.com/prometheus/common/expfmt/encode.go

@@ -18,7 +18,7 @@ import (
 	"io"
 	"net/http"
 
-	"github.com/matttproud/golang_protobuf_extensions/pbutil"
+	"github.com/matttproud/golang_protobuf_extensions/v2/pbutil"
 	"github.com/prometheus/common/internal/bitbucket.org/ww/goautoneg"
 	"google.golang.org/protobuf/encoding/prototext"