[SPARK-31527][SQL][TESTS][FOLLOWUP] Fix the number of rows in DateTimeBenchmark

### What changes were proposed in this pull request?
- Changed to the number of rows in benchmark cases from 3 to the actual number `N`.
- Regenerated benchmark results in the environment:

| Item | Description |
| ---- | ----|
| Region | us-west-2 (Oregon) |
| Instance | r3.xlarge |
| AMI | ubuntu/images/hvm-ssd/ubuntu-bionic-18.04-amd64-server-20190722.1 (ami-06f2f779464715dc5) |
| Java | OpenJDK 64-Bit Server VM 1.8.0_242 and OpenJDK 64-Bit Server VM 11.0.6+10 |

### Why are the changes needed?
The changes are needed to have:
- Correct benchmark results
- Base line for other perf improvements that can be checked in the same environment.

### Does this PR introduce _any_ user-facing change?
No

### How was this patch tested?
By running the benchmark and checking its output.

Closes #28440 from MaxGekk/SPARK-31527-DateTimeBenchmark-followup.

Authored-by: Max Gekk <[email protected]>
Signed-off-by: Takeshi Yamamuro <[email protected]>

Author: MaxGekk