Distributor failing to accept valid metric names

[anna-tran]

Describe the bug
When remote writing a metric such as "foo:bar", distributor fails with

failed to perform remote write. code: 400; message: sample invalid metric name: "foo:bar"

The : should be accepted in metric names.

To Reproduce
Steps to reproduce the behavior:

1. Start Cortex v1.20.0-rc.0
2. Remote write data with metric names including :

Expected behavior
No error on ingestion

Environment:

• Infrastructure: Kubernetes
• Deployment tool: Helm

Additional Context