## What changes were proposed in this pull request?

Since [Spark 1.6.0](https://github.com/apache/spark/commit/56d7da14ab8f89bf4f303b27f51fd22d23967ffb#diff-6f38a103058a6e233b7ad80718452387R96), there was a redundant '}' character in CTAS string plan's database argument string; `default}`. This PR aims to fix it.

**BEFORE**
```scala
scala> sc.version
res1: String = 1.6.0

scala> sql("create table t as select 1").explain
== Physical Plan ==
ExecutedCommand CreateTableAsSelect [Database:default}, TableName: t, InsertIntoHiveTable]
+- Project [1 AS _c0#3]
   +- OneRowRelation$
```

**AFTER**
```scala
scala> sql("create table t as select 1").explain
== Physical Plan ==
Execute CreateHiveTableAsSelectCommand CreateHiveTableAsSelectCommand [Database:default, TableName: t, InsertIntoHiveTable]
+- *(1) Project [1 AS 1#4]
   +- Scan OneRowRelation[]
```

## How was this patch tested?

Manual.

Closes #23064 from dongjoon-hyun/SPARK-FIX.

Authored-by: Dongjoon Hyun <dongjoon@apache.org>
Signed-off-by: hyukjinkwon <gurwls223@apache.org>
(cherry picked from commit b538c442cb3982cc4c3aac812a7d4764209dfbb7)
Signed-off-by: hyukjinkwon <gurwls223@apache.org>