It will not break the log chain (which I think is your goal), but it won't affect shrinking the log file. In order to shrink the log file (not recommended) you need to have the log backed up (ie remove the copy_only).
I do not recommend doing a backup to null though. You will not be able to recover in the event of an emergency.
What I would recommend (if you do need to shrink the log) is to do a tlog backup and then shrink the log file. Shrinking the log file will affect performance of the system though both during and possibly after if the log needs to grow again.
The above is all just my opinion on what you should do.
As with all advice you find on a random internet forum - you shouldn't blindly follow it. Always test on a test server to see if there is negative side effects before making changes to live!
I recommend you NEVER run "random code" you found online on any system you care about UNLESS you understand and can verify the code OR you don't care if the code trashes your system.