Fix grammar mistake
@@ -923,7 +923,7 @@ to access proxy statistics. These statistics are exposed at `/debug/vars` in JSO
## `prometheus`
-The `prometheus` option defines whether the prometheus metrics is enable, as well
+The `prometheus` option defines whether the prometheus metrics are enabled, as well
as the path to access the metrics.
>**NOTE**: The prometheus metrics do **not** cover pull-through cache statistics.
