remove some unused structs

src/renderer/Options.zig

@@ -20,12 +20,3 @@ surface_mailbox: apprt.surface.Mailbox,
 
 /// The apprt surface.
 rt_surface: *apprt.Surface,
-
-pub const Padding = struct {
-    // Explicit padding options, in pixels. The surface thread is
-    // expected to convert points to pixels for a given DPI.
-    explicit: renderer.Padding,
-
-    // Balance options
-    balance: bool = false,
-};