using service.name for check error logs

[juliaElastic]

Found that check error logs qg is failing as it is using service.type field by default to find fleet-server logs, which is not populated right now.
Using service.name instead.

Tested manually here: https://buildkite.com/elastic/serverless-quality-gates/builds/1182#018a603e-930f-4f87-b8d0-95e6524f21b7

$ ./observability/check-error-log-percentage.sh
--
  | % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
  | Dload  Upload   Total   Spent    Left  Speed
  | 100  1001  100   296  100   705    279    666  0:00:01  0:00:01 --:--:--   947
  | Calculated error percentage: 1

[elasticmachine]

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• Start Time: 2023-09-04T13:32:02.620+0000

• Duration: 34 min 26 sec

Test stats 🧪

Test	Results
Failed	0
Passed	815
Skipped	1
Total	816

💚 Flaky test report

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