test(args): add missing embed feature guard

[Xenira]

Fixes: #501

Description

Missing feature guard caused cargo test to fail linking.

Checklist

Check the boxes that apply (put an x in the brackets, like [x]). You can also check boxes after the PR is created.

• I have read the contribution guidelines.
• I have added tests that prove my code works as expected.
• I have added documentation if applicable.
• I have added a migration guide if applicable.

❤️ Thank you for your contribution!

[coveralls]

Pull Request Test Coverage Report for Build 16242244822

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 22.331%

---

Totals
Change from base Build 16203548003:	0.0%
Covered Lines:	870
Relevant Lines:	3896

---

💛 - Coveralls