unknown metric type return while using header 'Accept: application/openmetrics-text'

[GoneLikeAir]

Describe the bug
When I try to get metric from loki, I found that there are some metric with 'unknown' type.

To Reproduce
Steps to reproduce the behavior:
Using postman to reproduce:

1. Modify header: Accept: application/openmetrics-text
2. send request to ip:3100/metrics
   

Expected behavior
Expected all the metric types are correct(one of guage, counter, summary, histogram).

Environment:

• Infrastructure: Kubernetes
• Deployment tool: helm
• Version: 2.4.2

[stale]

Hi! This issue has been automatically marked as stale because it has not had any
activity in the past 30 days.

We use a stalebot among other tools to help manage the state of issues in this project.
A stalebot can be very useful in closing issues in a number of cases; the most common
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