The version of CocoaPods on the mac builders is 1.8.4

Fetching cocoapods 1.8.4
Installing cocoapods 1.8.4

https://logs.chromium.org/logs/flutter/buildbucket/cr-buildbucket.appspot.com/8864533259479547856/+/steps/Install_gems/0/steps/install_gems/0/stdout

Upgrade to version 1.9.3.

The tool will soon recommend a minimum of 1.9 #69807