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

Bumps [github.com/prometheus/client_golang](https://github.com/prometheus/client_golang) from 1.18.0 to 1.19.0.
- [Release notes](https://github.com/prometheus/client_golang/releases)
- [Changelog](https://github.com/prometheus/client_golang/blob/v1.19.0/CHANGELOG.md)
- [Commits](https://github.com/prometheus/client_golang/compare/v1.18.0...v1.19.0)

---
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>
(cherry picked from commit af228c847e)

vendor/github.com/prometheus/common/model/value_float.go

@@ -20,14 +20,12 @@ import (
 	"strconv"
 )
 
-var (
-	// ZeroSamplePair is the pseudo zero-value of SamplePair used to signal a
-	// non-existing sample pair. It is a SamplePair with timestamp Earliest and
-	// value 0.0. Note that the natural zero value of SamplePair has a timestamp
-	// of 0, which is possible to appear in a real SamplePair and thus not
-	// suitable to signal a non-existing SamplePair.
-	ZeroSamplePair = SamplePair{Timestamp: Earliest}
-)
+// ZeroSamplePair is the pseudo zero-value of SamplePair used to signal a
+// non-existing sample pair. It is a SamplePair with timestamp Earliest and
+// value 0.0. Note that the natural zero value of SamplePair has a timestamp
+// of 0, which is possible to appear in a real SamplePair and thus not
+// suitable to signal a non-existing SamplePair.
+var ZeroSamplePair = SamplePair{Timestamp: Earliest}
 
 // A SampleValue is a representation of a value for a given sample at a given
 // time.