Fix ST1016 linter staticcheck issues

[dsimansk]

For details check on the parent issue #4417

[Cali0707]

Fixing this issue involves re-enabling the ST1016 check in https://github.com/knative-extensions/eventing-kafka-broker/blob/main/.golangci.yaml, and fixing all associated linter errors for the check.

For more info on ST1016, read here: https://staticcheck.dev/docs/checks#ST1016

/triage accepted
/kind good-first-issue