[SPARK-25855][CORE][FOLLOW-UP] Format config name to follow the other boolean conf naming convention

### What changes were proposed in this pull request?

Change config name from `spark.eventLog.allowErasureCoding` to `spark.eventLog.allowErasureCoding.enabled`.

### Why are the changes needed?

To follow the other boolean conf naming convention.

### Does this PR introduce any user-facing change?

No, it's newly added in Spark 3.0.

### How was this patch tested?

Tested manually and pass Jenkins.

Closes apache#26998 from Ngone51/SPARK-25855-FOLLOWUP.

Authored-by: yi.wu <yi.wu@databricks.com>
Signed-off-by: Wenchen Fan <wenchen@databricks.com>

Author: Ngone51

core/src/main/scala/org/apache/spark/internal/config/package.scala

@@ -131,7 +131,7 @@ package object config {
       .createWithDefault(false)
 
   private[spark] val EVENT_LOG_ALLOW_EC =
-    ConfigBuilder("spark.eventLog.allowErasureCoding")
+    ConfigBuilder("spark.eventLog.erasureCoding.enabled")
       .booleanConf
       .createWithDefault(false)
 

docs/configuration.md

@@ -966,7 +966,7 @@ Apart from these, the following properties are also available, and may be useful
   </td>
 </tr>
 <tr>
-  <td><code>spark.eventLog.allowErasureCoding</code></td>
+  <td><code>spark.eventLog.erasureCoding.enabled</code></td>
   <td>false</td>
   <td>
     Whether to allow event logs to use erasure coding, or turn erasure coding off, regardless of