Revert "std: add accept_filter struct to make use of SO_ACCEPTFILTER socket option"

This reverts commit 1d322fe510.

lib/std/c/freebsd.zig

@@ -1105,11 +1105,6 @@ pub const DT = struct {
     pub const WHT = 14;
 };
 
-pub const accept_filter = extern struct {
-    af_name: [16]u8,
-    af_args: [240]u8,
-};
-
 /// add event to kq (implies enable)
 pub const EV_ADD = 0x0001;