Update misleading note in section-defining-outputs-for-jobs.md

[piotrekkr]

Why:

Because note about handling outputs when using strategy matrix is misleading and wrong in multiple places. Here is my overview of what is wrong:

1. $GITHUB_OUTPUT is shared between all steps in a job. If you use the same output name in multiple steps, the last step to write to the output will override the value

   This is simply not true. Each step has it's own unique outputs file that it can write to. Next steps cannot override previous step outputs which is even show in usage example.

2. If your job uses a matrix and writes to $GITHUB_OUTPUT, the content will be overwritten for each matrix combination.

   Using $GITHUB_OUTPUT does not override any job outputs. It can only set or override step outputs. Job need to define its own outputs and it can use steps context for this but this is not required for job outputs definition. Author of this note probably mixed step outputs with job outputs. Each job outputs inside matrix are combined, this is true, but author forgot to mention that last finished job in matrix will add new and override matching job outputs from all previous jobs.

3. You can use the matrix context to create unique output names for each job configuration. For more information, see "AUTOTITLE."

   There is no way to use contexts within job outputs names. I tested it and always had an error from GitHub when trying to run workflow. Something like this is not allowed:

   jobs:
     job1:
       runs-on: ubuntu-latest
       outputs:
         output_${{ matrix.job }}: ${{ steps.gen_output.outputs.output_1 }}
       strategy:
         matrix:
           job: [1, 2, 3]
   
   

What's being changed (if available, include any code snippets, screenshots, or gifs):

I've changed the note content and added an example of how matrix job outputs are combined.

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• I have reviewed my changes in staging, available via the View deployment link in this PR's timeline (this link will be available after opening the PR).

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Source	Preview	Production	What Changed
actions/using-jobs/defining-outputs-for-jobs.md	fpt ghec ghes@ 3.13 3.12 3.11 3.10 3.9	fpt ghec ghes@ 3.13 3.12 3.11 3.10 3.9	from reusable
actions/using-workflows/workflow-syntax-for-github-actions.md	fpt ghec ghes@ 3.13 3.12 3.11 3.10 3.9	fpt ghec ghes@ 3.13 3.12 3.11 3.10 3.9	from reusable

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fpt: Free, Pro, Team
ghec: GitHub Enterprise Cloud
ghes: GitHub Enterprise Server

[nguyenalex836]

@piotrekkr Thanks so much for opening a PR! I'll get this triaged for review ✨