README: fix markdown typo in document

[saracalihan]

I found a typo in the task list element in the "Closures" section and fixed it.

Before:

After:

[BuggieBot]

Hello!

One or more of the commit messages in this PR do not match the Jakt code submission policy, please check the lint_commits CI job for more details on which commits were flagged and why. Please do not close this PR and open another, instead modify your commit message(s) with git commit --amend and force push those changes to update this PR.

[alimpfard]

Hey, thanks for the PR. Please fix the commit message issue:

readme: Fix markdown typo in document (5f89b6f58db228e65f3620148d9e3c124a6a47d0): [...] First word of commit after the subsystem is not capitalized

I'd suggest "README: ..." or "Meta: Fix typo in readme"

[saracalihan]

Thanks for the suggestion, I fixed it as it should be