Update command to show expected output

[MekalBoy]

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

Calling strace -e clone ./sum_array_threads 2 would not show the clone3 syscall.
Replacing clone with clone,clone3 in both commands allows the syscalls to display as expected.

A small typo has also been fixed.

[teodutu]

This PR is almost OK. You only need to squash your commits into a single one. First run git rebase -i HEAD~2 then in the rebase menu, change the word pick from the last line into s, then save and exit. This will open another editor where you'll be see the messages of the 2 commits in this PR merged into a single one. There you'll need to delete the second commit message so that only the first one remains. Then use git push -f to update the remote branch.

[MekalBoy]

The two commits have been squashed into one and the commit description has been updated to keep a maximum of 75 characters per line.

[teodutu]

Great work. Thanks!