docs: add missing parenthesis

[smallwat3r]

Description

This PR closes a missing parenthesis in the usage docs.

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)

How Has This Been Tested?

Please describe the tests that you ran to verify your changes.

• Unit tests
• Spec Tests
• Integration tests / Manual Tests

Ran make html from the docs Makefile, and visualised the generated usage.html file.

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• 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
• Any dependent changes have been merged and published in downstream modules

[coveralls]

coverage: 96.898%. remained the same
when pulling bbce8f0 on smallwat3r:typo-fix
into aa25e16 on Unleash:main.

[sighphyre]

Nice catch, thank you!