[SPARK-15223][DOCS] fix wrongly named config reference

## What changes were proposed in this pull request?

The configuration setting `spark.executor.logs.rolling.size.maxBytes` was changed to `spark.executor.logs.rolling.maxSize` in 1.4 or so.

This commit fixes a remaining reference to the old name in the documentation.

Also the description for `spark.executor.logs.rolling.maxSize` was edited to clearly state that the unit for the size is bytes.

## How was this patch tested?

no tests

Author: Philipp Hoffmann <mail@philipphoffmann.de>

Closes #13001 from philipphoffmann/patch-3.

docs/configuration.md

@@ -284,7 +284,7 @@ Apart from these, the following properties are also available, and may be useful
   <td><code>spark.executor.logs.rolling.maxSize</code></td>
   <td>(none)</td>
   <td>
-    Set the max size of the file by which the executor logs will be rolled over.
+    Set the max size of the file in bytes by which the executor logs will be rolled over.
     Rolling is disabled by default. See <code>spark.executor.logs.rolling.maxRetainedFiles</code>
     for automatic cleaning of old logs.
   </td>
@@ -296,7 +296,7 @@ Apart from these, the following properties are also available, and may be useful
     Set the strategy of rolling of executor logs. By default it is disabled. It can
     be set to "time" (time-based rolling) or "size" (size-based rolling). For "time",
     use <code>spark.executor.logs.rolling.time.interval</code> to set the rolling interval.
-    For "size", use <code>spark.executor.logs.rolling.size.maxBytes</code> to set
+    For "size", use <code>spark.executor.logs.rolling.maxSize</code> to set
     the maximum file size for rolling.
   </td>
 </tr>