Fix build status badge

[lorenzodonini]

Proposed changes

Fixes build status badge. The badge now points to the test.yaml workflow.

Types of changes

What types of changes does your code introduce?

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation Update (if none of the other choices apply)