[SPARK-25933][DOCUMENTATION] Fix pstats.Stats() reference in configuration.md

## What changes were proposed in this pull request?

Change ptats.Stats() to pstats.Stats() for `spark.python.profile.dump` in configuration.md.

## How was this patch tested?

Doc test

Closes apache#22933 from AlexHagerman/doc_fix.

Authored-by: Alex Hagerman <[email protected]>
Signed-off-by: Sean Owen <[email protected]>
(cherry picked from commit 1a7abf3)
Signed-off-by: Sean Owen <[email protected]>

Author: Alex Hagerman

docs/configuration.md

@@ -445,7 +445,7 @@ Apart from these, the following properties are also available, and may be useful
   <td>
     The directory which is used to dump the profile result before driver exiting.
     The results will be dumped as separated file for each RDD. They can be loaded
-    by ptats.Stats(). If this is specified, the profile result will not be displayed
+    by <code>pstats.Stats()</code>. If this is specified, the profile result will not be displayed
     automatically.
   </td>
 </tr>