Missing "broader" subject headings

[Aaron Straup Cope]

$> go run -mod vendor cmd/parse-lcsh/main.go -include-all /usr/local/data/loc/lcsh.both.ndjson > lcsh.csv
$> grep sh85015274 lcsh.csv 
sh85015274,Boeing 727 (Jet transports),,,

Compared with:

https://id.loc.gov/authorities/subjects/sh85015274.html