react-instantsearch-router-nextjs wrong replace url on push

### 🐛 Current behavior

the fix on push method work on all the url, even on the domain part and not only on the path
```ts
push(newUrl) {
let url = newUrl
// We need to do this because there's an error when using i18n on the root path
// it says for example `pages/fr.js` doesn't exist
if (singletonRouter.locale) {
url = url.replace(`/${singletonRouter.locale}`, '');
}

// No need to provide the second argument, Next.js will know what to do
singletonRouter.push(url, undefined, {
shallow: true,
})
},
```

if the url is something like `https://it.mydomain.eu/product` with the locale part in third level domain, it will replace the url to `https://.mydomain.eu/product`

### 🔍 Steps to reproduce

1. has domain with locale part as third level (example https://it.mydomain.eu)
2. use createInstantSearchRouterNext of react-instantsearch-router-nextjs

### Live reproduction

unable to reproduce on codesandbox

### 💭 Expected behavior

should only replace the path part

### Possibile Solution

you can try with a regex like this: https://regex101.com/r/U8mzbj/1

```ts
push(newUrl) {
let url = newUrl
// We need to do this because there's an error when using i18n on the root path
// it says for example `pages/fr.js` doesn't exist
if (singletonRouter.locale) {
url = url.replace(new RegExp(`(?<=^https?:\/\/[^\/]+)\/${singletonRouter.locale}(?=\/|$)`, 'i'), '');
}

// No need to provide the second argument, Next.js will know what to do
singletonRouter.push(url, undefined, {
shallow: true,
})
},
```

### Package version

7.3.0

### Operating system

_No response_

### Browser

_No response_

### Code of Conduct

- [X] I agree to follow this project's Code of Conduct

Start from the push method in createInstantSearchRouterNext for react-instantsearch-router-nextjs and inspect how singletonRouter.locale is removed from newUrl. Reproduce with a locale in the hostname, such as https://it.mydomain.eu/product; done means only the path locale is removed and the domain remains unchanged.

Written by the indexing model from the issue text.