Remove `prometheus_nginxlog_exporter_container_image_registry_prefix_upstream`

Signed-off-by: Suguru Hirahara <did🔑z6MkvVZk1A3KBApWJXv2Ju4H14ErDfRGxh8zxdXSZ4vACDg5>

roles/custom/matrix-prometheus-nginxlog-exporter/defaults/main.yml

@@ -26,7 +26,6 @@ prometheus_nginxlog_exporter_container_syslog_port: '6514'
 prometheus_nginxlog_exporter_container_image_arch: ['amd64', 'arm64']
 prometheus_nginxlog_exporter_container_image: "{{ prometheus_nginxlog_exporter_container_image_registry_prefix }}martin-helmich/prometheus-nginxlog-exporter/exporter:{{ prometheus_nginxlog_exporter_container_image_tag }}"
 prometheus_nginxlog_exporter_container_image_registry_prefix: "{{ prometheus_nginxlog_exporter_container_image_registry_prefix_upstream }}"
-prometheus_nginxlog_exporter_container_image_registry_prefix_upstream: "{{ prometheus_nginxlog_exporter_container_image_registry_prefix_upstream_default }}"
 prometheus_nginxlog_exporter_container_image_registry_prefix_upstream_default: "ghcr.io/"
 prometheus_nginxlog_exporter_container_image_tag: "{{ 'latest' if prometheus_nginxlog_exporter_version == 'master' else prometheus_nginxlog_exporter_version }}-{{ matrix_architecture }}"
 prometheus_nginxlog_exporter_container_image_force_pull: "{{ prometheus_nginxlog_exporter_container_image.endswith(':latest') }}"