updates tests

Author: HyukjinKwon

sql/core/src/main/scala/org/apache/spark/sql/functions.scala

@@ -3906,7 +3906,6 @@ object functions {
    */
   def schema_of_csv(csv: String): Column = schema_of_csv(lit(csv))
 
-
   /**
    * Parses a CSV string and infers its schema in DDL format.
    *

sql/core/src/test/resources/sql-tests/results/csv-functions.sql.out

@@ -91,7 +91,7 @@ select schema_of_csv(null)
 struct<>
 -- !query 9 output
 org.apache.spark.sql.AnalysisException
-cannot resolve 'schema_of_csv(CAST(NULL AS STRING))' due to data type mismatch: The input csv should be a string literal and not null; however, got CAST(NULL AS STRING).; line 1 pos 7
+cannot resolve 'schema_of_csv(NULL)' due to data type mismatch: The input csv should be a string literal and not null; however, got NULL.; line 1 pos 7
 
 
 -- !query 10