reset_tz_after_tests

Author: B Vadlamani

datafusion/sqllogictest/test_files/spark/conversion/cast_int_to_timestamp.slt

@@ -191,7 +191,7 @@ SELECT spark_cast(1710057600::bigint, 'timestamp');
 ----
 2024-03-10T01:00:00-07:00
 
-# Reset to default UTC
+# Reset to default
 statement ok
 SET datafusion.execution.time_zone = 'UTC';
 
@@ -248,7 +248,7 @@ NULL NULL NULL NULL
 
 # Reset and cleanup
 statement ok
-SET datafusion.execution.time_zone = 'UTC';
+RESET datafusion.execution.time_zone;
 
 statement ok
 DROP TABLE int_test;