[SPARK-13400] Stop using deprecated Octal escape literals

## What changes were proposed in this pull request?

This removes the remaining deprecated Octal escape literals. The followings are the warnings on those two lines.
```
LiteralExpressionSuite.scala:99: Octal escape literals are deprecated, use \u0000 instead.
HiveQlSuite.scala:74: Octal escape literals are deprecated, use \u002c instead.
```

## How was this patch tested?

Manual.
During building, there should be no warning on `Octal escape literals`.
```
mvn -DskipTests clean install
```

Author: Dongjoon Hyun <dongjoon@apache.org>

Closes apache#11584 from dongjoon-hyun/SPARK-13400.

sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/expressions/LiteralExpressionSuite.scala

@@ -96,7 +96,7 @@ class LiteralExpressionSuite extends SparkFunSuite with ExpressionEvalHelper {
   test("string literals") {
     checkEvaluation(Literal(""), "")
     checkEvaluation(Literal("test"), "test")
-    checkEvaluation(Literal("\0"), "\0")
+    checkEvaluation(Literal("\u0000"), "\u0000")
   }
 
   test("sum two literals") {

sql/hive/src/test/scala/org/apache/spark/sql/hive/HiveQlSuite.scala

@@ -71,7 +71,7 @@ class HiveQlSuite extends SparkFunSuite with BeforeAndAfterAll {
       CatalogColumn("dt", "string", comment = Some("date type")) ::
       CatalogColumn("hour", "string", comment = Some("hour of the day")) :: Nil)
     assert(desc.storage.serdeProperties ==
-      Map((serdeConstants.SERIALIZATION_FORMAT, "\054"), (serdeConstants.FIELD_DELIM, "\054")))
+      Map((serdeConstants.SERIALIZATION_FORMAT, "\u002C"), (serdeConstants.FIELD_DELIM, "\u002C")))
     assert(desc.storage.inputFormat == Some("org.apache.hadoop.hive.ql.io.RCFileInputFormat"))
     assert(desc.storage.outputFormat == Some("org.apache.hadoop.hive.ql.io.RCFileOutputFormat"))
     assert(desc.storage.serde ==