[SPARK-28856][FOLLOW-UP][SQL][TEST] Add the namespaces keyword to TableIdentifierParserSuite

Author: hoffmann99

sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/parser/TableIdentifierParserSuite.scala

@@ -443,6 +443,7 @@ class TableIdentifierParserSuite extends SparkFunSuite with SQLHelper {
     "month",
     "months",
     "msck",
+    "namespaces",
     "natural",
     "no",
     "not",