You are almost there.
Unfortunately, the use of Threads.threadid() is no longer recommended due to the dynamical scheduling mechanisms that Threads.@threads offers.
You can read more about here PSA: Thread-local state is no longer recommended; Common misconceptions about threadid() and nthreads().
To get the version you have working, you have to update the for loop to read
Threads.@threads :static for i in 1:50
However, as the blog post explains this is also not longer recommended and one should use the advises given there.