Add Warbling Vireo to the list of lumped and split species for the 2026 and 2027 data release

[AdamCSmithCWS]

In the 2026 data release, warbling vireo will be treated as unidentified Eastern/Western Warbling Vireo.
In the 2027 data release, the two regional species will be split in some areas and not in others, so a more thoughtful approach will be necessary, potentially analysing only the lumped group.