Remove \n from errx and die messages

errx() already appends \n internally. "\n" in the error message will
result in a blank line after the message. die() is just a wrapper around
errx() so it receives the same treatment.

src/main.c

@@ -515,7 +515,7 @@ int main(int argc, char *argv[]) {
 
     conn = xcb_connect(NULL, &conn_screen);
     if (xcb_connection_has_error(conn))
-        errx(EXIT_FAILURE, "Cannot open display\n");
+        errx(EXIT_FAILURE, "Cannot open display");
 
     sndisplay = sn_xcb_display_new(conn, NULL, NULL);