memory leak if enable --collector.pbm at vesrion 0.44 not empty db(180mb, 10dbs). if empty exaple new cluster- not leak memory

[ldn7]

Describe the bug
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If the issue relates to PMM, please open JIRA PMM issue instead of GH issue.

To Reproduce
Steps to reproduce the behavior:

1. what parameters are being passed to mongodb_exporter
2. describe steps to reproduce the issue

if enable --collector.pbm increase memory

and incere on primary. shards or configure

Expected behavior
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Logs
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Environment

• OS, repository: "percona/mongodb_exporter" tag: "0.44"
• environment (docker, k8s, etc) k8s
• MongoDB version 8.0.11

Additional context
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