Update tracking for CVE-2019-17534/vips

Further investigation shows that actually no released version was ever
affected by the issue. The too early fetching of map was introduced in a
refactoring in a development version, and just noticed by the
oss-fuzzer, which got fixed the day after.

Thus the initial triage of the affectness was wrong, because in those
version for which #942254 was filled, there was not a problem with
fetching the map too early.