py/objstr: Remove duplicate % in error string.
The double-% was added in (Jun
2014) when such errors were formatted with printf.  But then
(Dec 2018) changed
mp_obj_new_exception_msg() to not format the message, as discussed
in  So such error strings are no longer formatted and a % is just
that.
@@ -1555,7 +1555,7 @@ STATIC mp_obj_t str_modulo_format(mp_obj_t pattern, size_t n_args, const mp_obj_
size_t slen;
const char *s = mp_obj_str_get_data(arg, &slen);
if (slen != 1) {
- mp_raise_TypeError("%%c needs int or char");
+ mp_raise_TypeError("%c needs int or char");
}
mp_print_strn(&print, s, 1, flags, ' ', width);
} else if (arg_looks_integer(arg)) {
