Test: only run wpa on PHP 7.2 to save resource

[dinhtungdu]

Description of the Change

I was wrong when I suggested running WPA on both 7.2 and 7.3. We only need to run that test one time because the PHP version is controlled by the snapshot, not the test environment. We can run WPA tests for other PHP versions by running tests against multiple snapshots.

Alternate Designs

Benefits

Save resources and build time.

Possible Drawbacks

Verification Process

Checklist:

• I have read the CONTRIBUTING document.
• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my change.
• All new and existing tests passed.

Applicable Issues

Changelog Entry

[johnwatkins0]

Good thinking, @dinhtungdu . We're learning as we go 😄 . I'm merging.