Make the note style consistent

Author: HyukjinKwon

docs/configuration.md

@@ -190,9 +190,10 @@ of the most common options to set are:
     and it is up to the application to avoid exceeding the overhead memory space
     shared with other non-JVM processes. When PySpark is run in YARN or Kubernetes, this memory
     is added to executor resource requests.
-
-    NOTE: Python memory usage may not be limited on platforms that do not support resource limiting, such as Windows.
-    NOTE: Python memory usage is dependent on Python's 'resource' module; therefore, the behaviors and limitations are inherited.
+    <br/>
+    <em>Note:</em> Python memory usage may not be limited on platforms that do not support resource limiting, such as Windows.
+    <br/>
+    <em>Note:</em> Python memory usage is dependent on Python's 'resource' module; therefore, the behaviors and limitations are inherited.
   </td>
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@@ -224,7 +225,8 @@ of the most common options to set are:
     stored on disk. This should be on a fast, local disk in your system. It can also be a
     comma-separated list of multiple directories on different disks.
 
-    NOTE: In Spark 1.0 and later this will be overridden by SPARK_LOCAL_DIRS (Standalone), MESOS_SANDBOX (Mesos) or
+    <br/>
+    <em>Note:</em> In Spark 1.0 and later this will be overridden by SPARK_LOCAL_DIRS (Standalone), MESOS_SANDBOX (Mesos) or
     LOCAL_DIRS (YARN) environment variables set by the cluster manager.
   </td>
 </tr>