evas pmap loader - remove pointless extra assign of end of string to 0

not an actual bug - just analysis impacting

found by PVS studio

src/modules/evas/image_loaders/pmaps/evas_image_load_pmaps.c

@@ -350,7 +350,6 @@ pmaps_buffer_plain_update(Pmaps_Buffer *b)
    b->unread[0] = '\0';
    b->unread_len = 0;
 
-   b->buffer[r] = '\0';
    b->current = b->buffer;
    b->end = b->buffer + r;