[MINOR][INFRA][DOCS] Remove undated comment in build_and_test.yml

[HyukjinKwon]

What changes were proposed in this pull request?

This PR removes outdated comment. We don't use branch-3.3 anymore

Why are the changes needed?

To remove obsolete information

Does this PR introduce any user-facing change?

No, dev-only.

How was this patch tested?

N/A

Was this patch authored or co-authored using generative AI tooling?

No.