Pull request review is triggered multiple times by the number of reviewers

I’m using this action to send some notifications to slack when a pull request must be reviewed by one or many of the devs.
This is the workflow I’m using, where I’m looping the requested_reviewers of the pull request based on the information returned by octokit/webhook.js

name: slack-notify-pr-review
on:
  pull_request:
    types: [review_requested]

jobs:
  slack-notify:
    runs-on: ubuntu-latest
    env:
      SLACK_WEBHOOK_URL: ${{ secrets.SLACK_WEBHOOK }}
    steps:
      - uses: act10ns/slack@v1.5.0
        with:
          status: ${{ job.status }}
          message: |
            *<{{refUrl}}|PR _{{description}}({{ref}})_ requires code review>*
            {{#if payload.pull_request.requested_reviewers }}
            *Please, the following users check the code and accept/reject accordingly:*
            {{#each payload.pull_request.requested_reviewers}}
            :white_check_mark: <{{this.url}}|`{{this.login}}`>
            {{/each}}
            {{/if}}
          channel: '#playground'

The problem comes when I create a pull request with multiple reviewers, as the action is triggered multiple times:

I wonder if anyone can think in a way to fix this. In the worst case, trigger the action multiple times, but mention in the message the sole reviewer that triggered the action.
I know that the action is using a kind-of-outdated octokit webhook version (7.15.1 when last version is 9.19.0), but probably it doesn’t have to do with the version more than how pull_request_reviewer works vs the available data in github API, but I’m just guessing here.