[MINOR] Improve SQLConf messages

### What changes were proposed in this pull request?
The current SQLConf messages of `spark.sql.hive.convertMetastoreParquet` and `spark.sql.hive.convertMetastoreOrc` are not very clear to end users. This PR is to improve them.

### How was this patch tested?
N/A

Author: gatorsmile <gatorsmile@gmail.com>

Closes #18657 from gatorsmile/msgUpdates.

sql/hive/src/main/scala/org/apache/spark/sql/hive/HiveUtils.scala

@@ -86,8 +86,8 @@ private[spark] object HiveUtils extends Logging {
     .createWithDefault("builtin")
 
   val CONVERT_METASTORE_PARQUET = buildConf("spark.sql.hive.convertMetastoreParquet")
-    .doc("When set to false, Spark SQL will use the Hive SerDe for parquet tables instead of " +
-      "the built in support.")
+    .doc("When set to true, the built-in Parquet reader and writer are used to process " +
+      "parquet tables created by using the HiveQL syntax, instead of Hive serde.")
     .booleanConf
     .createWithDefault(true)
 
@@ -101,8 +101,8 @@ private[spark] object HiveUtils extends Logging {
 
   val CONVERT_METASTORE_ORC = buildConf("spark.sql.hive.convertMetastoreOrc")
     .internal()
-    .doc("When set to false, Spark SQL will use the Hive SerDe for ORC tables instead of " +
-      "the built in support.")
+    .doc("When set to true, the built-in ORC reader and writer are used to process " +
+      "ORC tables created by using the HiveQL syntax, instead of Hive serde.")
     .booleanConf
     .createWithDefault(false)