date_trunc benchmark fails with a panic

[Omega359]

Describe the bug

Benchmarking date_trunc_minute_1000: Warming up for 3.0000 s
thread 'main' panicked at datafusion/functions/src/datetime/date_trunc.rs:149:16:
index out of bounds: the len is 1 but the index is 1
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

The line # may be off because I'm seeing this in a sidebranch I'm working on but I'm fairly certain this will happen in main too.

The issue is the return type is wrong in the benchmark

let return_type = &udf.return_type(&[timestamps.data_type()]).unwrap();

I think this was broken in #15049

To Reproduce

No response

Expected behavior

No response

Additional context

No response

[Omega359]

FYI @Blizzara

[Blizzara]

Oh, sad, I totally screwed this line up: https://github.com/apache/datafusion/pull/15049/files#diff-4e41ff9c31349a5ede5e9c4048505bdbd8183a23d88c20c5ae28028d66952bd9R49.

I'll put up a fix, thanks for flagging and sorry!