fix(curriculum/english): remove extra backtick in Modal Verbs task

[pulkitbajaj]

Removed an extra leading backtick in the "Learn How to Use Modal Verbs — Task 143" lesson so the Markdown renders correctly.

Checklist:

• I have read and followed the contribution guidelines.
• I have read and followed the how to open a pull request guide.
• My pull request targets the main branch of freeCodeCamp.
• I have tested these changes either locally on my machine, or GitHub Codespaces.

Closes freeCodeCamp#64086

[majestic-owl448]

this PR has been created on your own repo, not on freeCodeCamp's repo, if you want to contribute you need to create PRs on freeCodeCamp's repo

[pulkitbajaj]

Thanks for pointing that out earlier — it helped me fix the PR correctly!