[docs] Added line to PHP section of config

Summary: Included line from "macOS/Xcode updates" Notion doc

Test Plan: N/A

Reviewers: atul, palys-swm, ashoat

Reviewed By: palys-swm, ashoat

Subscribers: ashoat, palys-swm, Adrian, karol-bisztyga, benschac, boristopalov

Differential Revision: https://phabricator.ashoat.com/D2358