fix: updated message string in onboarding screen (#29286)

This PR is to update the onboarding screen message with proper
punctuation

## **Related issues**

Fixes: #26763 

## **Manual testing steps**

1. Go to onboarding
2. Check the message has proper punctuation on this screen

## **Screenshots/Recordings**

<!-- If applicable, add screenshots and/or recordings to visualize the
before and after of your change. -->

### **Before**
![Screenshot 2024-12-17 at 4 40
06 PM](https://github.com/user-attachments/assets/94bf0296-b412-460f-a136-034264d07140)


### **After**

![Screenshot 2024-12-17 at 4 39
51 PM](https://github.com/user-attachments/assets/bea72254-5479-4252-b2dc-03f0dac2316f)

## **Pre-merge author checklist**

- [ ] 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).
- [ ] I've completed the PR template to the best of my ability
- [ ] I’ve included tests if applicable
- [ ] I’ve documented my code using [JSDoc](https://jsdoc.app/) format
if applicable
- [ ] 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.