Github Actions: Clarify masking explanation in workflow-commands.md

[mcummings128]

Why:

Closes: TBD

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

In the Github Actions documentation Workflow commands for GitHub Actions: Masking A Value In A Log

This pull request clarifies that masking a value must be done once per value per job. This is not apparent enough in the documentation--while the warning is present, it doesn't specify this needs only to be done once per value per job, only that add-mask should be used with the value as soon as possible. Adding this sentence makes add-mask behavior more explicit and user-friendly.

Check off the following:

• A subject matter expert (SME) has reviewed the technical accuracy of the content in this PR. In most cases, the author can be the SME. Open source contributions may require an SME review from GitHub staff.
• The changes in this PR meet the docs fundamentals that are required for all content.
• All CI checks are passing and the changes look good in the review environment.

[github-actions]

How to review these changes 👓

Thank you for your contribution. To review these changes, choose one of the following options:

• Spin up a codespace
• Set up a local development environment

A Hubber will need to deploy your changes internally to review.

Table of review links

Note: Please update the URL for your staging server or codespace.

The table shows the files in the content directory that were changed in this pull request. This helps you review your changes on a staging server. Changes to the data directory are not included in this table.

Source	Review	Production	What Changed
actions/reference/workflows-and-actions/workflow-commands.md	fpt ghec ghes@ 3.20 3.19 3.18 3.17 3.16	fpt ghec ghes@ 3.20 3.19 3.18 3.17 3.16

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

🤖 This comment is automatically generated.