sub: remove unused sub_bitmaps.scaled field

sub/osd.c

@@ -436,5 +436,4 @@ void osd_rescale_bitmaps(struct sub_bitmaps *imgs, int frame_w, int frame_h,
         bi->dw = (int)(bi->w * xscale + 0.5);
         bi->dh = (int)(bi->h * yscale + 0.5);
     }
-    imgs->scaled = xscale != 1 || yscale != 1;
 }

sub/osd.h

@@ -58,10 +58,6 @@ struct sub_bitmaps {
 
     enum sub_bitmap_format format;
 
-    // If false, dw==w && dh==h.
-    // SUBBITMAP_LIBASS is never scaled.
-    bool scaled;
-
     struct sub_bitmap *parts;
     int num_parts;