fix: only select commits ahead of main branch for gitleaks

mentioned in merge request gitlab-com/runbooks!4913 (merged)

mentioned in merge request cmbr!93 (merged)

mentioned in merge request bigquery-loader!48 (merged)

mentioned in merge request terra-transformer!108 (merged)

mentioned in merge request asdf-gl-infra!14 (merged)

mentioned in merge request common-ci-tasks-images!10 (merged)

mentioned in merge request !196 (merged)

mentioned in merge request third-party-container-images!11 (merged)

mentioned in merge request fluentd-docker!18 (closed)

mentioned in merge request gitlab-com/gl-infra/k8s-workloads/common!178 (merged)

mentioned in merge request slackline!95 (merged)

mentioned in merge request woodhouse!187 (merged)

mentioned in merge request gitlab-org/release-tools!1992 (merged)

mentioned in merge request fluentd-docker!22 (closed)

mentioned in merge request fluentd-docker!27 (merged)

mentioned in merge request gitlab-com/gl-infra/platform/runway/runwayctl!2 (merged)

mentioned in merge request gcp-quota-exporter!2 (merged)