[8.x] Set MGet as the claim strategy for serverless (#194694) (#196349)

# Backport

This will backport the following commits from `main` to `8.x`:
- [Set MGet as the claim strategy for serverless
(#194694)](#194694)

<!--- Backport version: 9.4.3 -->

### Questions ?
Please refer to the [Backport tool
documentation](https://github.com/sqren/backport)

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Co-authored-by: Mike Côté <mikecote@users.noreply.github.com>

config/serverless.yml

@@ -202,6 +202,7 @@ uiSettings:
     labs:dashboard:deferBelowFold: false
 
 # Task Manager
+xpack.task_manager.claim_strategy: mget
 xpack.task_manager.allow_reading_invalid_state: false
 xpack.task_manager.request_timeouts.update_by_query: 60000
 xpack.task_manager.metrics_reset_interval: 120000