Fix formatted iterable index argument not accounting for a current-value-holding-iterable correctly

[shtaif]

Fixes the following issue regarding formatting async iterables with current values with iterateFormatted's index argument.

Given an async iterable myIter that starts with a current value of '*' and yields 'a' and then 'b';

before the fix we will observe:

<It>{iterateFormatted(myIter, (val, i) => `${val}_${i}`)}</It>

/*
  Will render:

  '*_0' and then
  'a_0' and then
  'b_1'
*/

after the fix we will observe:

<It>{iterateFormatted(myIter, (val, i) => `${val}_${i}`)}</It>

/*
  Will render:

  '*_0' and then
  'a_1' and then
  'b_2'
*/