Editorial: Update a step-reference.

PR tc39#1938 (among other things) modified the steps of
Number.prototype.toExponential, but didn't update
the step-reference in the following Note.

spec.html

@@ -27234,7 +27234,7 @@ <h1>Number.prototype.toExponential ( _fractionDigits_ )</h1>
           1. Return the string-concatenation of _s_ and _m_.
         </emu-alg>
         <emu-note>
-          <p>For implementations that provide more accurate conversions than required by the rules above, it is recommended that the following alternative version of step 10.b.i be used as a guideline:</p>
+          <p>For implementations that provide more accurate conversions than required by the rules above, it is recommended that the following alternative version of step 9.b.i be used as a guideline:</p>
           <emu-alg type="i">
             1. Let _e_, _n_, and _f_ be integers such that _f_ &ge; 0, 10<sup>_f_</sup> &le; _n_ &lt; 10<sup>_f_ + 1</sup>, the Number value for ℝ(_n_) &times; 10<sub>ℝ</sub><sup>ℝ(_e_) - ℝ(_f_)</sup> is _x_, and _f_ is as small as possible. If there are multiple possibilities for _n_, choose the value of _n_ for which ℝ(_n_) &times; 10<sub>ℝ</sub><sup>ℝ(_e_) - ℝ(_f_)</sup> is closest in value to _x_. If there are two such possible values of _n_, choose the one that is even.
           </emu-alg>