MINOR: contrib/prometheus-exporter: add uweight field

this field was added in commit bd7151002437af1a034a9fdbb582b3cbef5a78d1
("MINOR: stats: report server's user-configured weight next to effective
weight")

Signed-off-by: William Dauchy <wdauchy@gmail.com>
diff --git a/contrib/prometheus-exporter/service-prometheus.c b/contrib/prometheus-exporter/service-prometheus.c
index ff27df6..debe2f6 100644
--- a/contrib/prometheus-exporter/service-prometheus.c
+++ b/contrib/prometheus-exporter/service-prometheus.c
@@ -280,6 +280,7 @@
 	[ST_F_SAFE_CONN_CUR]=   { .n = IST("safe_idle_connections_current"),    .type = PROMEX_MT_GAUGE,    .flags = (                                                 PROMEX_FL_SRV_METRIC) },
 	[ST_F_USED_CONN_CUR]  = { .n = IST("used_connections_current"),         .type = PROMEX_MT_GAUGE,    .flags = (                                                 PROMEX_FL_SRV_METRIC) },
 	[ST_F_NEED_CONN_EST]  = { .n = IST("need_connections_current"),         .type = PROMEX_MT_GAUGE,    .flags = (                                                 PROMEX_FL_SRV_METRIC) },
+	[ST_F_UWEIGHT]        = { .n = IST("uweight"),                          .type = PROMEX_MT_GAUGE,    .flags = (                         PROMEX_FL_BACK_METRIC | PROMEX_FL_SRV_METRIC) },
 };
 
 /* Description of overriden stats fields */