[truetype] Allow linear scaling for unhinted rendering (#50470). * src/truetype/ttdriver.c (tt_size_request): Revert change from 2011-07-16; the intended metrics fix seems now to be implemented in a different way, making the patch unnecessary. Note that this change was usually patched out by all major GNU/Linux distributions due to heavy side effects. * src/truetype/ttgload.c (compute_glyph_metrics, TT_Load_Glyph): Refer to the metrics of the `TT_Size' object.