[Couchbase] Fix flaky system test issue

[Linu-Elias]

Proposed commit message

Checklist

• I have reviewed tips for building integrations and this pull request is aligned with them.
• I have verified that all data streams collect metrics or logs.
• I have added an entry to my package's changelog.yml file.
• I have verified that Kibana version constraints are current according to guidelines.
• I have verified that any added dashboard complies with Kibana's Dashboard good practices

Author's Checklist

• [ ]

How to test this PR locally

Related issues

• Closes-
  [Stack 9.4.0-SNAPSHOT] [couchbase] Failing test daily: system test: default (variant: v7.1.0) in couchbase.cache #16920
  [Stack 9.4.0-SNAPSHOT] [couchbase] Failing test daily: system test: default (variant: v7.1.0) in couchbase.bucket #16735
  [Stack 8.19.9-SNAPSHOT] [couchbase] Failing test daily: system test: default (variant: v7.1.0) in couchbase.query_index #16700
  [Subscription basic] [couchbase] Failing test daily: system test: default (variant: v7.1.0) in couchbase.node #16656

Screenshots

[elastic-vault-github-plugin-prod]

🚀 Benchmarks report

Package couchbase 👍(2) 💚(0) 💔(8)

Expand to view

Data stream	Previous EPS	New EPS	Diff (%)	Result
xdcr	26315.79	20000	-6315.79 (-24%)	💔
cache	20000	16129.03	-3870.97 (-19.35%)	💔
cluster	16949.15	11764.71	-5184.44 (-30.59%)	💔
database_stats	33333.33	27027.03	-6306.3 (-18.92%)	💔
miscellaneous	17543.86	11764.71	-5779.15 (-32.94%)	💔
node	10309.28	7299.27	-3010.01 (-29.2%)	💔
query_index	21739.13	8928.57	-12810.56 (-58.93%)	💔
resource	22222.22	18181.82	-4040.4 (-18.18%)	💔

To see the full report comment with /test benchmark fullreport

[elasticmachine]

💚 Build Succeeded

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• Commit: a78e7ff

cc @Linu-Elias