Tests: Prevent filename conflict on @actions/upload-artifact

[tbradsha]

This changes the project name in the E2E matrix from Jetpack Boost - Concatenate JS/CSS to Jetpack Boost - Concatenate JS and CSS.

Why? If a E2E project has a name deemed invalid by @actions/upload-artifact, it'll fail to upload that artifact (and subsequent ones), e.g.:

https://github.com/Automattic/jetpack/actions/runs/11645549949

Error: The artifact name is not valid: test-output-Jetpack Boost - Concatenate JS/CSS. Contains the following character:  Forward slash /
          
Invalid characters include:  Double quote ", Colon :, Less than <, Greater than >, Vertical bar |, Asterisk *, Question mark ?, Carriage return \r, Line feed \n, Backslash \, Forward slash /

Solving this took me down a rabbit hole (e.g. looking in the actual test name rather than the matrix, checking for upload-artifact rename abilities, GH Actions string manipulation in expression syntax). This seems to be the best and simplest solution.

Other information:

• Have you written new tests for your changes, if applicable?
• Have you checked the E2E test CI results, and verified that your changes do not break them?
• Have you tested your changes on WordPress.com, if applicable (if so, you'll see a generated comment below with a script to run)?

Jetpack product discussion

Does this pull request change what data or activity we track or use?

Testing instructions:

Confirm artifacts are properly uploaded:
https://github.com/Automattic/jetpack/actions/runs/11672407033?pr=40042

[github-actions]

Thank you for your PR!

When contributing to Jetpack, we have a few suggestions that can help us test and review your patch:

• ✅ Include a description of your PR changes.
  
• ✅ Add a "[Status]" label (In Progress, Needs Team Review, ...).
  
• ✅ Add testing instructions.
  
• ✅ Specify whether this PR includes any changes to data or privacy.
  
• ✅ Add changelog entries to affected projects
  

This comment will be updated as you work on your PR and make changes. If you think that some of those checks are not needed for your PR, please explain why you think so. Thanks for cooperation 🤖

---

The e2e test report can be found here. Please note that it can take a few minutes after the e2e tests checks are complete for the report to be available.

---

Follow this PR Review Process:

1. Ensure all required checks appearing at the bottom of this PR are passing.
2. Choose a review path based on your changes:
   • A. Team Review: add the "[Status] Needs Team Review" label
     • For most changes, including minor cross-team impacts.
     • Example: Updating a team-specific component or a small change to a shared library.
   • B. Crew Review: add the "[Status] Needs Review" label
     • For significant changes to core functionality.
     • Example: Major updates to a shared library or complex features.
   • C. Both: Start with Team, then request Crew
     • For complex changes or when you need extra confidence.
     • Example: Refactor affecting multiple systems.
3. Get at least one approval before merging.

Still unsure? Reach out in #jetpack-developers for guidance!

---

Boost plugin:

• Next scheduled release: none scheduled.

If you have any questions about the release process, please ask in the #jetpack-releases channel on Slack.

[anomiex]

Thanks, I've been meaning to look into this but have never gotten around to it.

For comparison, the similar .github/files/generate-ci-matrix.php script for our Tests workflow has a separate "artifact" property that it by default generates from the name and includes some tests to catch if anyone accidentally adds something with an invalid character.