[8.7](backport #35159) [Filebeat][envoyproxy] Fix JSON formatting in envoyproxy testing logs

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This is an automatic backport of pull request #35159 done by Mergify.

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• Start Time: 2023-04-21T13:19:09.876+0000

• Duration: 77 min 13 sec

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Test	Results
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Total	3039

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