Fix: flush stdout in print_table

This fixes the output of print_table during the optimization so that it
works in Jupyter notebooks or when piping output to a file (e.g., on a
cluster) by flushing stdout after each iteration.

Without this, nothing was being printed while the optimization was still
running.

src/optimize.jl

@@ -315,4 +315,5 @@ function print_table(wrk, iteration, args...)
         print(lpad(str, w))
     end
     print("\n")
+    flush(stdout)
 end