fix: fixed getStakingNavbar broken back and cancel buttons regression (…

…#12920)

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## **Description**
This PR fixes a recently introduced regression that broke the "back" and
"cancel" buttons when using `getStakingNavbar()`. This only impacted the
staking views.

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Write a short description of the changes included in this pull request,
also include relevant motivation and context. Have in mind the following
questions:
1. What is the reason for the change?
2. What is the improvement/solution?
-->

## **Related issues**

- Ticket that introduced regression: [Stake-884: Add more mobile pooled
staking
events](https://consensyssoftware.atlassian.net/browse/STAKE-884)
- PR that introduced regression:
#12651


## **Manual testing steps**

Stake Input Screen (broken cancel navbar button)
1. Set `MM_POOLED_STAKING_UI_ENABLED` to `true` in `.js.env`
2. Click "Ethereum" from the token list (home screen)
3. Click on the "Stake" or "Stake more" button (the same can be tested
for the unstake flow if you have ETH staked)
4. From the Staking Input View, click the "Cancel" button in the
top-right corner.
5. You should be redirected to the previous screen (Ethereum details)

Stake Confirmation Screen (broken back navbar button)
1. Set `MM_POOLED_STAKING_UI_ENABLED` to `true` in `.js.env`
2. Click "Ethereum" from the token list (home screen)
3. Click on the "Stake" or "Stake more" button (the same can be tested
for the unstake flow if you have ETH staked)
4. Enter a valid amount and press "Review" to view the stake
confirmation screen.
5. Click the "back" button in the top-left corner in the navbar
6. You should be redirected to the previous screen (stake input screen)



## **Screenshots/Recordings**

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before and after of your change. -->

### **Before**

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https://github.com/user-attachments/assets/6b626874-7bee-4f32-a352-1a48e105eeb1


### **After**

<!-- [screenshots/recordings] -->

https://github.com/user-attachments/assets/7e12e943-bcc1-4f35-89c6-531185a83cd1

## **Pre-merge author checklist**

- [x] I’ve followed [MetaMask Contributor
Docs](https://github.com/MetaMask/contributor-docs) and [MetaMask Mobile
Coding
Standards](https://github.com/MetaMask/metamask-mobile/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
- [ ] 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-mobile/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.

app/components/UI/Navbar/index.js

@@ -1991,7 +1991,7 @@ export function getStakingNavbar(
       withMetaMetrics(navigationPop, {
         event: metricsOptions.backButtonEvent.event,
         properties: metricsOptions.backButtonEvent.properties,
-      });
+      })();
     } else {
       navigationPop();
     }
@@ -2002,7 +2002,7 @@ export function getStakingNavbar(
       withMetaMetrics(navigationPop, {
         event: metricsOptions.cancelButtonEvent.event,
         properties: metricsOptions.cancelButtonEvent.properties,
-      });
+      })();
     } else {
       navigationPop();
     }