Fix --require-full-match on inline snapshots with leading newlines

[max-sixty]

Otherwise --force-update-snapshots would never be satisfied.

Note comment inline: rather than spend more time on this, let's just try and get one of those two in:

                // Note that we previously would match the exact values of the
                // unnormalized text. But that's too strict — it means we can
                // never match a snapshot that has leading/trailing whitespace.
                // So instead we check it matches on the latest format.
                // Generally those should be the same — latest should be doing
                // the minimum normalization; if they diverge we could update
                // this to be stricter.
                //
                // (I think to do this perfectly, we'd want to match the
                // _reference_ value unnormalized, but the _generated_ value
                // normalized. That way, we can get the But at the moment we
                // don't distinguish between which is which in our data
                // structures.)