[GCP] Fix kubernetes.io service prefix indendation

[ghost]

What does this PR do?

Fixes kubernetes.io service prefix indentation.

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.

Author's Checklist

• [ ]

How to test this PR locally

Related issues

Screenshots

[endorama]

This error is affecting other data streams as well (tested with compute and dataproc). I've no idea why this would "leak" to other data streams.

Trying to add an integration from Kibana UI resulted in this error:

bad indentation of a mapping entry at line 8, column 28: service_metric_prefix: kubernetes.io/ ^

[elasticmachine]

🚀 Benchmarks report

Package gcp 👍(0) 💚(0) 💔(5)

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Data stream	Previous EPS	New EPS	Diff (%)	Result
audit	1915.71	1474.93	-440.78 (-23.01%)	💔
dns	2739.73	1782.53	-957.2 (-34.94%)	💔
firewall	3174.6	1972.39	-1202.21 (-37.87%)	💔
loadbalancing_logs	4878.05	3412.97	-1465.08 (-30.03%)	💔
vpcflow	4166.67	2192.98	-1973.69 (-47.37%)	💔

To see the full report comment with /test benchmark fullreport

[elasticmachine]

💚 Build Succeeded

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Build stats

• Start Time: 2022-09-30T09:26:00.186+0000

• Duration: 20 min 32 sec

Test stats 🧪

Test	Results
Failed	0
Passed	82
Skipped	0
Total	82

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[elasticmachine]

🌐 Coverage report

Name	Metrics % (covered/total)	Diff
Packages	100.0% (5/5)	💚
Files	100.0% (5/5)	💚 2.792
Classes	100.0% (5/5)	💚 2.792
Methods	90.816% (89/98)	👍 1.222
Lines	95.752% (1375/1436)	👍 4.217
Conditionals	100.0% (0/0)	💚