macos: remove the ability to bind fn/globe

This was recently introduced a few days ago. Unfortunately, this doesn't
work as expected. The "function" modifier is not actually the fn key
but used by macOS to represent a variety of "functional" key presses.
This breaks other bindings such as #2411.

I can't find a source on the internet that reliably tells me how we
can detect fn key presses, but I do find a number of sources that tell
us we can't.

src/input/KeyEncoder.zig

@@ -35,8 +35,6 @@ pub fn encode(
     self: *const KeyEncoder,
     buf: []u8,
 ) ![]const u8 {
-    // log.debug("encode {}", .{self.*});
-
     if (self.kitty_flags.int() != 0) return try self.kitty(buf);
     return try self.legacy(buf);
 }