cherry-pick(release-v1.3.x): Fixed the type of execution_timestamp

[service-binding-operator-bot]

Changes

Changed the type of execution_timestamp parameter to string while sending the data to opensearch. So that it is consistent with upload_time parameter.

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[openshift-ci]

[APPROVALNOTIFIER] This PR is APPROVED

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The full list of commands accepted by this bot can be found here.

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