add 'pull_request' to the ns_test and sbt_test workflow triggers

[hcannoodt]

Describe your changes

Run tests on PR creation.
Only running on push isn't enough when dealing with PRs from forks.

Related issue(s)

Closes #xxxx

Type of Change

• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• New functionality (non-breaking change which adds functionality)
• Major change (non-breaking change which modifies existing functionality)
• Minor change (non-breaking change which does not modify existing functionality)
• Bug fix (non-breaking change which fixes an issue)
• This change requires a documentation update

Checklist

Requirements:

• I have read the CONTRIBUTING doc.
• I have performed a self-review of my code by checking the "Changed Files" tab.
• My code follows the code style of this project.

Tests:

• I have added tests that prove my fix is effective or that my feature works.
• New and existing unit tests pass locally with my changes.

Documentation:

• Proposed changes are described in the CHANGELOG.md.
• I have updated the documentation accordingly.

Test Environment

[rcannood]

Minor question