bar_cmd_font: fix leak of font

join_args is a freshly allocated string and can be used as is.

Found through static analysis.

sway/commands/bar/font.c

@@ -14,7 +14,7 @@ struct cmd_results *bar_cmd_font(int argc, char **argv) {
 	}
 	char *font = join_args(argv, argc);
 	free(config->current_bar->font);
-	config->current_bar->font = strdup(font);
+	config->current_bar->font = font;
 	wlr_log(L_DEBUG, "Settings font '%s' for bar: %s",
 			config->current_bar->font, config->current_bar->id);
 	return cmd_results_new(CMD_SUCCESS, NULL, NULL);