https://linear.app/comm/issue/ENG-10205/update-flow-to-02691
v0.248.0: Support for long deprecated predicate function (%checks) is removed. It will still parse, but all of them will error with unsupported-syntax, and %checks will be completely ignored for type checking purpose as if it doesn't exist.
Replaced with type guards in D15039, D15065
Depends on D15026