Updated grafana dashboard with dynamic rate_interval

- added in one place the rate_interval variable instead of static "[1m]".

Change-Id: Id437523cc4d610bad79f612701a111a6b03994ea
Related-Bug: PROD-30422
(cherry picked from commit 41d31d33354eeff85cd65b78fae0d5af274172b1)
diff --git a/apache/files/grafana_dashboards/apache_prometheus.json b/apache/files/grafana_dashboards/apache_prometheus.json
index d72da30..fcecdce 100644
--- a/apache/files/grafana_dashboards/apache_prometheus.json
+++ b/apache/files/grafana_dashboards/apache_prometheus.json
@@ -1769,7 +1769,7 @@
       "steppedLine": false,
       "targets": [
         {
-          "expr": "irate(apache_TotalkBytes{host=~\"$host\"}[1m])",
+          "expr": "irate(apache_TotalkBytes{host=~\"$host\"}[$rate_interval])",
           "format": "time_series",
           "intervalFactor": 2,
           "legendFormat": "{{ host }}",