runtime: remove duplicate declarations of SetFinalizer/KeepAlive

These should have been removed in CL 38794.  It's a bug that the
compiler even permits these duplicate declarations.

Change-Id: I6499588e8cc0e784344f10755d293eef9b5f9bb9
Reviewed-on: https://go-review.googlesource.com/41134
Reviewed-by: Than McIntosh <thanm@google.com>
1 file changed