Fix NaN issue in Product Tour Popover (#23100)

## **Description**
The Popover is displaying NaN because the '/' was not being treated as a
string.
Fixed that and added a test to help prevent it in the future.
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## **Related issues**

Fixes:
https://github.com/MetaMask/metamask-extension/pull/22905/files#r1498090474

## **Manual testing steps**

1. Fresh install of metamask, open popup
2. Verify that the product tour popover starts by displaying 1/3
3. run tests with `yarn jest
ui/components/multichain/product-tour-popover/product-tour-popover.test.js`
4. Verify new test passes 'should render correct steps' or fails under
the right circumstances

## **Screenshots/Recordings**

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

### **Before**

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

### **After**

<!-- [screenshots/recordings] -->
<img width="353" alt="image"
src="https://github.com/MetaMask/metamask-extension/assets/10986371/dfd8e9d8-a8db-4426-aea9-5208fa2a24d7">


## **Pre-merge author checklist**

- [ ] I’ve followed [MetaMask Coding
Standards](https://github.com/MetaMask/metamask-extension/blob/develop/.github/guidelines/CODING_GUIDELINES.md).
- [ ] I've clearly explained what problem this PR is solving and how it
is solved.
- [ ] I've linked related issues
- [ ] I've included manual testing steps
- [ ] I've included screenshots/recordings if applicable
- [ ] 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/develop/.github/guidelines/LABELING_GUIDELINES.md)).
Not required for external contributors.
- [ ] I’ve properly set the pull request status:
  - [ ] In case it's not yet "ready for review", I've set it to "draft".
- [ ] In case it's "ready for review", I've changed it from "draft" to
"non-draft".

## **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.

ui/components/multichain/product-tour-popover/product-tour-popover.js

@@ -110,9 +110,10 @@ export const ProductTour = ({
             paddingTop={2}
             color={TextColor.infoInverse}
             variant={TextVariant.bodyMd}
+            data-testid="multichain-product-tour-menu-popover-step-counter"
           >
             {currentStep && totalSteps
-              ? { currentStep } / { totalSteps }
+              ? `${currentStep} / ${totalSteps}`
               : null}
           </Text>
           <ButtonBase

ui/components/multichain/product-tour-popover/product-tour-popover.test.js

@@ -28,4 +28,16 @@ describe('DetectedTokensBanner', () => {
     );
     expect(prevIcon).toBeInTheDocument();
   });
+  it('should render correct steps', () => {
+    const { getByText } = render(
+      <ProductTour
+        anchorElement={document.body}
+        {...props}
+        prevIcon
+        currentStep={2}
+        totalSteps={5}
+      />,
+    );
+    expect(getByText('2 / 5')).toBeInTheDocument();
+  });
 });