Fixed a typo

Author: liyinan926

docs/user-guide.md

@@ -24,6 +24,8 @@ also refer to the [GCP guide](gcp.md).
     * [Using Secrets As Environment Variables](#using-secrets-as-environment-variables)
     * [Using Image Pull Secrets](#using-image-pull-secrets)
     * [Using Pod Affinity](#using-pod-affinity)
+    * [Python Support](#python-support)
+    * [Monitoring](#monitoring) 
 * [Working with SparkApplications](#working-with-sparkapplications)
     * [Creating a New SparkApplication](#creating-a-new-sparkapplication)
     * [Deleting a SparkApplication](#deleting-a-sparkapplication)
@@ -402,7 +404,7 @@ and currently requires building a custom Docker image from the Spark master bran
 
 The Spark Operator supports using the Spark metric system to expose metrics to a varity of sinks. Particularly, it is able to automatically configure the metric system to expose metrics to [Prometheus](https://prometheus.io/). Specifically, the field `.spec.monitoring` specifies how application monitoring is handled and particularly how metrics are to be reported. The metric system is configured through the configuration file `metrics.properties`, which gets its content from the field `.spec.monitoring.metricsProperties`. The content of [metrics.properties](../spark-docker/conf/metrics.properties) will be used by default if `.spec.monitoring.metricsProperties` is not specified. You can choose to enable or disable reporting driver and executor metrics using the fields `.spec.monitoring.exposeDriverMetrics` and `.spec.monitoring.exposeExecutorMetrics`, respectively. 
 
-Further, the field `.spec.monitoring.prometheus` specifies how metrics are exposed to Prometheus using the [Prometheus JMX exporter](https://github.com/prometheus/jmx_exporter). When `.spec.monitoring.prometheus` is specified, the operator automatically configures the JMX exporter to run as a Java agent. The only required field of `.spec.monitoring.prometheus` is `jmxExporterJar`, which specified the path to the Prometheus JMX exporter Java agent jar in the container. If you use the image `gcr.io/spark-operator/spark:v2.3.1-gcs-prometheus`, the jar is located at `/prometheus/jmx_prometheus_javaagent-0.3.1.jar`. The field `.spec.monitoring.prometheus.port` specifies the port the JMX exporter Java agent binds to and defaults to `8090` if not specified. The field `.spec.monitoring.prometheus.configuration` specifies the content of the configuration to be used with the JMX exporter. The content of [metrics.properties](../spark-docker/conf/prometheus.yaml) will be used by default if `.spec.monitoring.prometheus.configuration` is not specified.    
+Further, the field `.spec.monitoring.prometheus` specifies how metrics are exposed to Prometheus using the [Prometheus JMX exporter](https://github.com/prometheus/jmx_exporter). When `.spec.monitoring.prometheus` is specified, the operator automatically configures the JMX exporter to run as a Java agent. The only required field of `.spec.monitoring.prometheus` is `jmxExporterJar`, which specified the path to the Prometheus JMX exporter Java agent jar in the container. If you use the image `gcr.io/spark-operator/spark:v2.3.1-gcs-prometheus`, the jar is located at `/prometheus/jmx_prometheus_javaagent-0.3.1.jar`. The field `.spec.monitoring.prometheus.port` specifies the port the JMX exporter Java agent binds to and defaults to `8090` if not specified. The field `.spec.monitoring.prometheus.configuration` specifies the content of the configuration to be used with the JMX exporter. The content of [prometheus.yaml](../spark-docker/conf/prometheus.yaml) will be used by default if `.spec.monitoring.prometheus.configuration` is not specified.    
 
 Below is an example that shows how to configure the metric system to expose metrics to Prometheus using the Prometheus JMX exporter. Note that the JMX exporter Java agent jar is listed as a dependency and will be downloaded to where `.spec.dep.jarsDownloadDir` points to in Spark 2.3.x, which is `/var/spark-data/spark-jars` by default. Things will be different in Spark 2.4 as dependencies will be downloaded to the local working directory instead in Spark 2.4. A complete example can be found in [examples/spark-pi-prometheus.yaml](../examples/spark-pi-prometheus.yaml).