chore: Improve background RPC timeout error message (#38564)

## **Description**

The error message for the `getState` timeout (from UI to background) has
been re-worded to avoid misleading users into thinking that the error
relates to network RPC endpoints. The current message has repeatedly
been confused because we typically use the term "RPC" to refer to
network RPC endpoints.

[![Open in GitHub
Codespaces](https://github.com/codespaces/badge.svg)](https://codespaces.new/MetaMask/metamask-extension/pull/38564?quickstart=1)

## **Changelog**

CHANGELOG entry: Improve error message when UI can't retrieve state from
background process

## **Related issues**

N/A

## **Manual testing steps**

I am not sure how best to reproduce this error, but it's just a copy
change so I'm not sure we strictly need to manually test this.

## **Screenshots/Recordings**

N/A

## **Pre-merge author checklist**

- [x] I've followed [MetaMask Contributor
Docs](https://github.com/MetaMask/contributor-docs) and [MetaMask
Extension Coding
Standards](https://github.com/MetaMask/metamask-extension/blob/main/.github/guidelines/CODING_GUIDELINES.md).
- [x] I've completed the PR template to the best of my ability
- [x] I’ve included tests if applicable
- [x] I’ve documented my code using [JSDoc](https://jsdoc.app/) format
if applicable
- [x] I’ve applied the right labels on the PR (see [labeling
guidelines](https://github.com/MetaMask/metamask-extension/blob/main/.github/guidelines/LABELING_GUIDELINES.md)).
Not required for external contributors.

## **Pre-merge reviewer checklist**

- [ ] I've manually tested the PR (e.g. pull and build branch, run the
app, test code being changed).
- [ ] I confirm that this PR addresses all acceptance criteria described
in the ticket it closes and includes the necessary testing evidence such
as recordings and or screenshots.

<!-- CURSOR_SUMMARY -->
---

> [!NOTE]
> Updates the background RPC client’s getState timeout error message and
aligns the unit test expectation.
> 
> <sup>Written by [Cursor
Bugbot](https://cursor.com/dashboard?tab=bugbot) for commit
e06819c. This will update automatically
on new commits. Configure
[here](https://cursor.com/dashboard?tab=bugbot).</sup>
<!-- /CURSOR_SUMMARY -->

Author: Gudahtt

app/scripts/lib/metaRPCClientFactory.test.js

@@ -179,7 +179,9 @@ describe('metaRPCClientFactory', () => {
     );
 
     jest.runOnlyPendingTimers();
-    await expect(errorPromise).rejects.toThrow('No response from RPC');
+    await expect(errorPromise).rejects.toThrow(
+      `Background 'getState' call exceeded timeout`,
+    );
 
     jest.useRealTimers();
   });

app/scripts/lib/metaRPCClientFactory.ts

@@ -186,7 +186,7 @@ export class MetaRPCClient<Api extends FunctionRegistry<Api>> {
         if (payload.method === 'getState') {
           timer = setTimeout(() => {
             this.requests.delete(payload.id);
-            reject(new Error('No response from RPC'));
+            reject(new Error(`Background 'getState' call exceeded timeout`));
           }, SIXTEEN_SECONDS_AS_MILLISECONDS);
         }
         this.requests.set(payload.id, { resolve, reject, timer });