i3bar: don't parse markup on statusline by default

fixes #1565

i3bar/src/child.c

@@ -164,9 +164,6 @@ static int stdin_start_map(void *context) {
     /* Default width of the separator block. */
     ctx->block.sep_block_width = logical_px(9);
 
-    /* Use markup by default */
-    ctx->block.is_markup = true;
-
     return 1;
 }