Remove unneeded comment from examples/expr2.py

We support the `if __name__ == "__main__"` syntax now

Author: ubaidsk

examples/expr2.py

@@ -1,10 +1,9 @@
+from lpython import i32
+
 def main0():
     x: i32
     x = (2+3)*5
     print(x)
 
-main0()
-
-# Not implemented yet in LPython:
-#if __name__ == "__main__":
-#    main()
+if __name__ == "__main__":
+   main0()