Editorial: Properly title-case the clause title ...

... "Applying the `**` operator"

Fixes #376.

spec.html

@@ -12770,7 +12770,7 @@ <h1>Applying the `%` Operator</h1>
         </ul>
       </emu-clause>
       <emu-clause id="sec-applying-the-exp-operator">
-        <h1>Applying the `**` operator</h1>
+        <h1>Applying the `**` Operator</h1>
         <p>
           Returns an implementation-dependent approximation of the result of raising _base_ to the power _exponent_.
         </p>