Build www/gotosocial on aarch64

Index: Makefile
===================================================================
RCS file: /cvs/ports/www/gotosocial/Makefile,v
retrieving revision 1.16
diff -u -p -r1.16 Makefile
--- Makefile 11 Nov 2023 02:51:03 -0000 1.16
+++ Makefile 31 Dec 2023 15:13:41 -0000
@@ -1,5 +1,4 @@
-# has deps that can build only on OpenBSD/amd64
-ONLY_FOR_ARCHS = amd64
+ONLY_FOR_ARCHS = amd64 aarch64

COMMENT = ActivityPub social network server

Just built this on arm64, seems to be running fine as well.

Unfortunately I'm not experienced with Go port maintenance, otherwise I
would have updated to 0.13.0 as well.