InList: don't need to treat Null as UTF8 data type

[liukun4515]

From this test case, we can know that we should not treat Null as UTF8 data type

Originally posted by @liukun4515 in #2764 (comment)

From the implemention:

1. https://github.com/apache/arrow-datafusion/blob/3da59e8877620a095efae102b0177e7e6a76f65b/datafusion/physical-expr/src/expressions/in_list.rs#L163

2. https://github.com/apache/arrow-datafusion/blob/3da59e8877620a095efae102b0177e7e6a76f65b/datafusion/physical-expr/src/expressions/in_list.rs#L111

[liukun4515]

duplicated with #2782