Typo in Number.prototype.toExponential

[jorendorff]

https://tc39.es/ecma262/#sec-number.prototype.toexponential

step 10.a.i reads:

1. Let e and n be integers such that 10^f ≤ n < 10^{f + 1} and for which n × 10^{e - n} - x is as close to zero as possible. If there are two such sets of e and n, pick the e and n for which n × 10^{e - f} is larger.

This can't be right.

Example: Suppose x, the number we're trying to format, is 123, and f = fractionDigits = 2. The correct output would be "1.23e2", which happens if this step selects n = 123 and e = 2. But the method described above selects n = 123 and e = 125.

It seems to be a typo introduced in #1135. _n_ &times; 10<sup>_e_ - _n_</sup> - _x_ should be changed back to _n_ &times; 10<sup>_e_ - _f_</sup> - _x_.