chore: remove unused CONNECTION_READY event (MetaMask#33163)

## **Description**

Removes unused `CONNECTION_READY` event from our code.


Here are all the places in the code, including in `node_modules` that
`CONNECTION_READY` appears. It is only ignored, never listened to or
otherwise used.


![image](https://github.com/user-attachments/assets/abafcb71-2047-4481-8dfa-17eb721108fb)


[![Open in GitHub
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Author: davidmurdoch

app/scripts/lib/stream-utils.js

@@ -1,8 +1,6 @@
 import ObjectMultiplex from '@metamask/object-multiplex';
 import { pipeline } from 'readable-stream';
 
-import { EXTENSION_MESSAGES } from '../../../shared/constants/app';
-
 /**
  * Sets up stream multiplexing for the given stream
  *
@@ -11,12 +9,6 @@ import { EXTENSION_MESSAGES } from '../../../shared/constants/app';
  */
 export function setupMultiplex(connectionStream) {
   const mux = new ObjectMultiplex();
-  /**
-   * We are using this streams to send keep alive message between backend/ui without setting up a multiplexer
-   * We need to tell the multiplexer to ignore them, else we get the " orphaned data for stream " warnings
-   * https://github.com/MetaMask/object-multiplex/blob/280385401de84f57ef57054d92cfeb8361ef2680/src/ObjectMultiplex.ts#L63
-   */
-  mux.ignoreStream(EXTENSION_MESSAGES.CONNECTION_READY);
   pipeline(connectionStream, mux, connectionStream, (err) => {
     // For context and todos related to the error message match, see https://github.com/MetaMask/metamask-extension/issues/26337
     if (err && !err.message?.match('Premature close')) {

app/scripts/ui.js

@@ -94,7 +94,7 @@ async function start() {
 
   /*
    * In case of MV3 the issue of blank screen was very frequent, it is caused by UI initialising before background is ready to send state.
-   * Code below ensures that UI is rendered only after "CONNECTION_READY" or "startUISync"
+   * Code below ensures that UI is rendered only after "startUISync"
    * messages are received thus the background is ready, and ensures that streams and
    * phishing warning page load only after the "startUISync" message is received.
    * In case the UI is already rendered, only update the streams.

shared/constants/app.ts

@@ -82,7 +82,6 @@ export const SMART_TRANSACTION_CONFIRMATION_TYPES = {
  * Custom messages to send and be received by the extension
  */
 export const EXTENSION_MESSAGES = {
-  CONNECTION_READY: 'CONNECTION_READY',
   READY: 'METAMASK_EXTENSION_READY',
 } as const;