ISSUE-16046: The new Docbot spams PRs with multiple comments

[sijie]

Original Issue: apache#16046

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Describe the bug
The new Docbot (apache#15797) added in apache#16027 spams PRs with multiple comments.

To Reproduce
There's an example in apache#16045
https://github.com/apache/pulsar/actions/workflows/ci-documentbot.yml

Example jobs:

Logs:
https://github.com/apache/pulsar/runs/6874257583?check_suite_focus=true
https://github.com/apache/pulsar/runs/6874257484?check_suite_focus=true
https://github.com/apache/pulsar/runs/6874256005?check_suite_focus=true

Expected behavior
The docbot shouldn't spam users with the same nagging message multiple times on the same PR.

Additional context
You can find workflow runs in https://github.com/apache/pulsar/actions/workflows/ci-documentbot.yml .
The workflow has been disabled until the problem is solved.