Improve comment in gram.y.
"As so-and-so" isn't bad English, but it has a faintly archaic
whiff to it, and confuses some non-native speakers. Write
"Like so-and-so" instead.
Per complaint from Tatsuo Ishii.
Discussion: https://postgr.es/m/
20240623.130154.
1867056921698616251.t-ishii@sranhm.sra.co.jp.sranhm