Remove 4 from new gv_autoload4_(sv|pvn?) functions

Remove 4 from new gv_autoload4_(sv|pvn?) functions

The 4 was added in commit 54310121b442 (inseparable changes during
5.003/4 developement), presumably the ‘Don't look up &AUTOLOAD in @ISA
when calling plain function’ part.

Before that, gv_autoload had three arguments, so the 4 indicated the
new version (with the method argument).

Since these new functions don’t all have four arguments, and since
they have a new naming convention, there is not reason for the 4.