MINOR: remove unused comment_bot.yml from CI scripts

[alamb]

Which issue does this PR close?

re #2149

Rationale for this change

This is some sort of action which helps with some process that is not relevant to the Rust implementation of Arrow. It is left over from when we pulled out the Rust code from the main arrow repo (it got copied from https://github.com/apache/arrow/blob/master/.github/workflows/comment_bot.yml)

It does run but doesn't do anything: https://github.com/apache/arrow-rs/actions/workflows/comment_bot.yml

What changes are included in this PR?

delete unused action

Are there any user-facing changes?

no

[ursabot]

Benchmark runs are scheduled for baseline = b8fd432 and contender = 87b19f8. 87b19f8 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-rs-commits is not supported on ec2-t3-xlarge-us-east-2] ec2-t3-xlarge-us-east-2
[Skipped ⚠️ Benchmarking of arrow-rs-commits is not supported on test-mac-arm] test-mac-arm
[Skipped ⚠️ Benchmarking of arrow-rs-commits is not supported on ursa-i9-9960x] ursa-i9-9960x
[Skipped ⚠️ Benchmarking of arrow-rs-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