io/drills: Fix internal and deployment broken references

[levitatie]

• Internal reference path for the I/O multiplexing page was wrong, it now links to the correct markdown file
• Deployment reference link to the I/O multiplexing page is now stripped of the / in the title variable since docusaurus strips punctuation in links by default

Prerequisite Checklist

• Read the contribution guidelines regarding submitting new changes to the project;
• Tested your changes against relevant architectures and platforms;
• Updated relevant documentation (if needed).

Description of changes

• Internal reference path for the I/O multiplexing page was wrong, it now links to the correct markdown file
• Deployment reference link to the I/O multiplexing page is now stripped of the / in the title variable since docusaurus strips punctuation in links by default