prometheus: Use new flag for enabling remote write receiver[1]

[1] https://github.com/prometheus/prometheus/commit/8fdfa52976ebb0c0594962fe4dac7605373fa638

roles/prometheus/templates/prometheus.conf.j2

 {% if prometheus_receive_only %}
-PROMETHEUS_ARGS="--storage.tsdb.retention.time=365d --enable-feature=remote-write-receiver --web.config.file=/etc/prometheus/web-config.yml --web.listen-address={{ wireguard_address }}:9090"
+PROMETHEUS_ARGS="--storage.tsdb.retention.time=365d --web.enable-remote-write-receiver --web.config.file=/etc/prometheus/web-config.yml --web.listen-address={{ wireguard_address }}:9090"
 {% else %}
 PROMETHEUS_ARGS="--storage.tsdb.retention.time=365d"
 {% endif %}