Update on "[compiler] Special-case phi inference for mixed readonly type"

This allows us to handle common operations such as `useFragment(...).edges.nodes ?? []` where we have a `Phi(MixedReadonly, Array)`. The underlying pattern remains general-purpose and not Relay-specific, and any API that returns transitively "mixed" data (primitives, arrays, plain objects) can benefit from the same type refinement.

[ghstack-poisoned]

Author: josephsavona

compiler/packages/babel-plugin-react-compiler/src/TypeInference/InferTypes.ts

@@ -14,9 +14,7 @@ import {
   Identifier,
   IdentifierId,
   Instruction,
-  isArrayType,
   makeType,
-  ObjectType,
   PropType,
   Type,
   typeEquals,