Replace unmaintained dependency gopkg.in/yaml.v2 with go.yaml.in/yaml/v4

[gab-arrobo]

No description provided.

[Copilot]

Pull Request Overview

This PR updates the project's YAML dependency from the unmaintained gopkg.in/yaml.v2 to the actively maintained go.yaml.in/yaml/v4 library to improve security and maintainability.

• Replaces import statement from gopkg.in/yaml.v2 to go.yaml.in/yaml/v4 in metricfunc.go
• Updates go.mod to use v4.0.0-rc.2 of the new YAML library and removes the old v2 dependency

Reviewed Changes

Copilot reviewed 2 out of 3 changed files in this pull request and generated no comments.

File	Description
metricfunc.go	Updates import statement to use the new YAML v4 library
go.mod	Adds new YAML v4 dependency and removes the old v2 dependency

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