MongoDB, slow chunk Migration for collection `config.system.sessions` with removing Shard - Config server relation

## Deployment
Sharded Cluster with 3 shards + 1 config server. (Note: each component has replication enabled, but only one replica)

## Action
Remove the shard that hosts `config.system.sessions` collection

## Problem
Drainage takes 20-25minutes

## Context
[MongoDB Forum Post](https://www.mongodb.com/community/forums/t/slow-drainage-of-collection-config-system-sessions-when-performing-removeshard/250904)
[Stack Overflow Post](https://stackoverflow.com/questions/77364840/mongodb-slow-chunk-migration-for-collection-config-system-sessions-with-remov)

Start with the linked MongoDB Forum and Stack Overflow posts, then reproduce shard removal on the described three-shard, one-config-server topology. The issue names no repository file, test, or acceptance criterion; completion would require a confirmed explanation for the 20–25 minute drainage and a defined resolution.

Written by the indexing model from the issue text.