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/Binding.zig

@@ -901,8 +901,6 @@ pub const Trigger = struct {
                 .{ "opt", "alt" },
                 .{ "option", "alt" },
                 .{ "control", "ctrl" },
-                .{ "fn", "function" },
-                .{ "globe", "function" },
             };
             inline for (alias_mods) |pair| {
                 if (std.mem.eql(u8, part, pair[0])) {

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);
 }

src/input/key.zig

@@ -89,11 +89,10 @@ pub const Mods = packed struct(Mods.Backing) {
     ctrl: bool = false,
     alt: bool = false,
     super: bool = false,
-    function: bool = false,
     caps_lock: bool = false,
     num_lock: bool = false,
     sides: side = .{},
-    _padding: u5 = 0,
+    _padding: u6 = 0,
 
     /// Tracks the side that is active for any given modifier. Note
     /// that this doesn't confirm a modifier is pressed; you must check
@@ -131,7 +130,6 @@ pub const Mods = packed struct(Mods.Backing) {
             .ctrl = self.ctrl,
             .alt = self.alt,
             .super = self.super,
-            .function = self.function,
         };
     }