Use consistent name for TimeUnit::Millisecond

[alamb]

Which issue does this PR close?

Part of #3531

Rationale for this change

As pointed out by @waitingkuo on https://github.com/apache/arrow-datafusion/pull/3534/files#r975610617 the naming of the TimeUnit enum in protobuf was not consistent with the arrow Schema leading to confusing

What changes are included in this PR?

1. Rename TimeUnit::TimeMillisecond to TimeUnit::Millisecond to be consistent with arrow

Are there any user-facing changes?

No

[ursabot]

Benchmark runs are scheduled for baseline = 52ff7ca and contender = add10a6. add10a6 is a master commit associated with this PR. Results will be available as each benchmark for each run completes.
Conbench compare runs links:
[Skipped ⚠️ Benchmarking of arrow-datafusion-commits is not supported on ec2-t3-xlarge-us-east-2] ec2-t3-xlarge-us-east-2
[Skipped ⚠️ Benchmarking of arrow-datafusion-commits is not supported on test-mac-arm] test-mac-arm
[Skipped ⚠️ Benchmarking of arrow-datafusion-commits is not supported on ursa-i9-9960x] ursa-i9-9960x
[Skipped ⚠️ Benchmarking of arrow-datafusion-commits is not supported on ursa-thinkcentre-m75q] ursa-thinkcentre-m75q
Buildkite builds:
Supported benchmarks:
ec2-t3-xlarge-us-east-2: Supported benchmark langs: Python, R. Runs only benchmarks with cloud = True
test-mac-arm: Supported benchmark langs: C++, Python, R
ursa-i9-9960x: Supported benchmark langs: Python, R, JavaScript
ursa-thinkcentre-m75q: Supported benchmark langs: C++, Java