Update dashboard

Author: ishanjainn

nginx-mixin/.lint

@@ -5,3 +5,9 @@ exclusions:
     reason: "Units are undefined where panel description is clear, and the entity being graphed is not available in default set of available units."
   template-datasource-rule:
     reason: "mixtool upgrade made this rule stricter. TODO: Fix errors and remove the warning exclusion"
+  template-job-rule:
+    reason: "NGINX Overview dashboard does not use a job label"
+  target-job-rule:
+    reason: "NGINX Overview dashboard does not use a job label"
+  target-rate-interval-rule:
+    reason: "using $__rate_interval breaks the dashboard hence using [5m] instead"