docs: workhorse metrics are not enabled by default

Summary

The documentation says that metrics should be enabled by default for workhorse, but they aren't.

https://gitlab.com/gitlab-org/charts/gitlab/-/blob/0d2c4c26acbad430bef4a8d1136b2f6dbc539ec8/charts/gitlab/charts/webservice/values.yaml#L235

Steps to reproduce

N/A

Configuration used

N/A

Current behavior

Workhorse metrics are not enabled by default.

Expected behavior

Workhorse metrics should be enabled by default

Versions

• Chart: v8.1.2
• Platform: N/A
• Kubernetes: N/A
• Helm: N/A

Relevant logs

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