Transform $ReadOnlyMap to ReadonlyMap (#55110)

Summary:
Pull Request resolved: #55110

We are transforming the following utility types to be more consistent with typescript and better AI integration:

* `$NonMaybeType` -> `NonNullable`
* `$ReadOnly` -> `Readonly`
* `$ReadOnlyArray` -> `ReadonlyArray`
* `$ReadOnlyMap` -> `ReadonlyMap`
* `$ReadOnlySet` -> `ReadonlySet`
* `$Keys` -> `keyof`
* `$Values` -> `Values`
* `mixed` -> `unknown`

See details in https://fb.workplace.com/groups/flowlang/permalink/1837907750148213/.

drop-conflicts

Command:

`js1 flow-runner codemod flow/transformUtilityType --format-files=false --legacy-type='$ReadOnlyMap'`

Changelog: [Internal]

Reviewed By: SamChou19815

Differential Revision: D90425806

fbshipit-source-id: e725c86053879a571b36aaeae1154d779571b362

Author: marcoww6

packages/dev-middleware/src/inspector-proxy/Device.js

@@ -96,7 +96,7 @@ export default class Device {
   #deviceSocket: WS;
 
   // Stores the most recent listing of device's pages, keyed by the `id` field.
-  #pages: $ReadOnlyMap<string, Page> = new Map();
+  #pages: ReadonlyMap<string, Page> = new Map();
 
   // Stores information about currently connected debugger (if any).
   #debuggerConnection: ?DebuggerConnection = null;