[MINOR][DOC][SQL] Fix two documents regarding size in bytes

## What changes were proposed in this pull request?

Fix two places in SQLConf documents regarding size in bytes and statistics.

## How was this patch tested?
No. Just change document.

Author: Liang-Chi Hsieh <simonh@tw.ibm.com>

Closes #14341 from viirya/fix-doc-size-in-bytes.

sql/core/src/main/scala/org/apache/spark/sql/internal/SQLConf.scala

@@ -109,7 +109,9 @@ object SQLConf {
     .doc("Configures the maximum size in bytes for a table that will be broadcast to all worker " +
       "nodes when performing a join.  By setting this value to -1 broadcasting can be disabled. " +
       "Note that currently statistics are only supported for Hive Metastore tables where the " +
-      "command<code>ANALYZE TABLE &lt;tableName&gt; COMPUTE STATISTICS noscan</code> has been run.")
+      "command<code>ANALYZE TABLE &lt;tableName&gt; COMPUTE STATISTICS noscan</code> has been " +
+      "run, and file-based data source tables where the statistics are computed directly on " +
+      "the files of data.")
     .longConf
     .createWithDefault(10L * 1024 * 1024)
 
@@ -122,10 +124,10 @@ object SQLConf {
 
   val DEFAULT_SIZE_IN_BYTES = SQLConfigBuilder("spark.sql.defaultSizeInBytes")
     .internal()
-    .doc("The default table size used in query planning. By default, it is set to a larger " +
-      "value than `spark.sql.autoBroadcastJoinThreshold` to be more conservative. That is to say " +
-      "by default the optimizer will not choose to broadcast a table unless it knows for sure " +
-      "its size is small enough.")
+    .doc("The default table size used in query planning. By default, it is set to Long.MaxValue " +
+      "which is larger than `spark.sql.autoBroadcastJoinThreshold` to be more conservative. " +
+      "That is to say by default the optimizer will not choose to broadcast a table unless it " +
+      "knows for sure its size is small enough.")
     .longConf
     .createWithDefault(-1)