subpicture: remove old plaintext member

Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

include/vlc_subpicture.h

@@ -65,7 +65,6 @@ struct subpicture_region_t
     int             i_alpha;                               /**< transparency */
 
     text_segment_t  *p_text;         /**< subtitle text, made of a list of segments */
-    char            *psz_text;       /**< text string comprising this region */
     char            *psz_html;       /**< HTML version of subtitle (NULL = use psz_text) */
     text_style_t    *p_style;        /**< a description of the text style formatting */
     bool            b_renderbg;      /**< render black background under text */