The logging level for the Jenkins Conjur plugin is currently set to INFO for all log messages. So as the plugin is currently designed, it would be an all-or-none choice for Conjur plugin logs being generated.
I don’t have access to a Jenkins server to try this, but you may be able to change the Conjur plugin logging level from the Jenkins UI (see Configure Loggers for Jenkins – CloudBees Support) to WARNING to quiesce the Conjur plugin log messages.
By the way, the following log in your output has been removed from the Conjur plugin, so you can eliminate that line from your logs by updating to a newer version of the Conjur plugin:
04-Jan-2021 17:00:00.000 INFO [Executor #-1 for master : executing BranchIndexing[prod/object]] org.conjur.jenkins.conjursecrets.ConjurSecretUsernameCredentialsImpl.getUsername Get UserName => jenkins