GitHub Actions - "Node.js 12 actions are deprecated." although I upgraded everything to v18

I get the warning

Node.js 12 actions are deprecated. 
For more information see: https://github.blog/changelog/2022-09-22-github-actions-all-actions-will-begin-running-on-node16-instead-of-node12/. 
Please update the following actions to use Node.js 16: ./

I know it's because v12 has been deprecated and is being removed, but I've changed my usages from v12 to v18 and I don't understand why I still get this warning. It should have vanished.

I've read the doc for Actions Maintainers at https://docs.github.com/en/actions/creating-actions/metadata-syntax-for-github-actions#runs-for-javascript-actions

• I only specify a nodejs version there: https://github.com/UnlyEd/github-action-await-vercel/blob/main/.github/workflows/update-codeclimate-coverage.yml#L24
• I use "@actions/core": "1.10.0"

I faced this issue when deploying a NextJS application using GitHub actions.

My job looked like this:

jobs:
  build:
    runs-on: ubuntu-latest
    steps:
      - name: Checkout code
        uses: actions/checkout@v2

The issue was with the actions/checkout@v2 which had be deprecated. All I had to do was to upgrade to actions/checkout@v3. So my job looked like this next:

jobs:
  build:
    runs-on: ubuntu-latest
    steps:
      - name: Checkout code
        uses: actions/checkout@v3

Resources: Example: Using versioned actions

While writing the question, I noticed in https://docs.github.com/en/actions/creating-actions/metadata-syntax-for-github-actions#runs-for-javascript-actions that there was a runs:. I had seen it, and overlooked it.

I didn't understood it was located in the /action.yml, at the root.

Here is an example: https://github.com/UnlyEd/github-action-await-vercel/blob/cee5b33a0725899c2a78be7d73819114f6aac745/action.yml#L17

Changing this line obviously fixed the issue.

I faced the same issue in my Next.js project.

I could resolve this issue by setting node-version as 16 in the GitHub workflow/*.yml file.
For example:

jobs:
  bulid:
    name: Production
    # The type of runner that the job will run on
    runs-on: ubuntu-latest

    # Steps represent a sequence of tasks that will be executed as part of the job
    steps:
      # Checks-out your repository under $GITHUB_WORKSPACE, so your job can access it
      - uses: actions/checkout@v2

      - name: Set up Node.js
        uses: actions/setup-node@v2
        with:
          node-version: 16