[Monitor] All properties of activityLogs_API.json spec EventData type should be read only

EventData type is only used as a return value for Listing activity logs which should not be modifyable on the client side. Please fix all of them by adding "readOnly": true, attribute to each property.

Open activityLogs_API.json and locate the EventData type. Review every property in that type and compare the specification with the issue's read-only requirement. Done means all EventData properties are marked read-only in the API specification; check the repository's specification validation process if one is available.

Written by the indexing model from the issue text.