[inplace.vector.modifiers] Revert wording for the Returns of try_append_range?

[hewillk]

The wording of Returns for try_append_range in the original paper is:

Returns: Iterator past last inserted element of rg.

It was changed after 37a6c0d to:

Returns: An iterator pointing to the first element of rg that was not inserted into *this, or ranges​::​end(rg) if no such element exists.

This doesn't seem right because ranges::end might be different than ranges::begin making it impossible to convert to borrowed_iterator_t<R>. Given that there is no description for such a situation in the [container] as described in [algorithm#requirements-13]:

In the description of algorithm return values, a sentinel value s denoting the end of a range [i, s) is sometimes returned where an iterator is expected. In these cases, the semantics are as if the sentinel is converted into an iterator using ranges​::​next(i, s).

Should we revert the current wording to make it consistent with the original wording?

@jwakely @tkoeppe

[jwakely]

How about:

The first iterator in the range ranges::begin(rg) + [0,n) that was not inserted into *this, where n is the number of elements in rg.