[BUG] The incorrect splicing of the GitHub API results in empty data from the request.

Hey there, I recently tried the demo [codelab-android-paging/tree/main/advanced/start](https://github.com/android/codelab-android-paging/tree/main/advanced/start), and found the list always empty, according to the [latest official document](https://docs.github.com/en/rest/search/search?apiVersion=2022-11-28#search-repositories) the reason is the `apiQuery` used in both start and end project missed a `+` between `query` and `IN_QUALIFIER`:

as in the start project:

IN_QUALIFIER:

https://github.com/android/codelab-android-paging/blob/d1f28e0caf76e429c31b063163cd0ad963b549c9/advanced/start/app/src/main/java/com/example/android/codelabs/paging/api/GithubService.kt#L27

`apiQuery`:

https://github.com/android/codelab-android-paging/blob/d1f28e0caf76e429c31b063163cd0ad963b549c9/advanced/start/app/src/main/java/com/example/android/codelabs/paging/data/GithubRepository.kt#L80

Same code in [codelab-android-paging/tree/main/advanced/end](https://github.com/android/codelab-android-paging/tree/main/advanced/end)

https://github.com/android/codelab-android-paging/blob/d1f28e0caf76e429c31b063163cd0ad963b549c9/advanced/end/app/src/main/java/com/example/android/codelabs/paging/api/GithubService.kt#L27

https://github.com/android/codelab-android-paging/blob/d1f28e0caf76e429c31b063163cd0ad963b549c9/advanced/end/app/src/main/java/com/example/android/codelabs/paging/data/GithubRemoteMediator.kt#L85

if we input a `query` as "Android", the final network request URL will be "https://api.github.com/search/repositories?sort=stars&q=Androidin%3Aname%2Cdescription&page=1&per_page=30"

and the result:

```
{
"total_count": 0,
"incomplete_results": false,
"items": [

]
}
```

after we add a `+` :

"https://api.github.com/search/repositories?sort=stars&q=Android%2Bin%3Aname%2Cdescription&page=1&per_page=30"

and the result:
```
{
"total_count": 64,
"incomplete_results": false,
"items": [
...
]
}
```

Start with advanced/start/app/src/main/java/com/example/android/codelabs/paging/data/GithubRepository.kt and advanced/end/app/src/main/java/com/example/android/codelabs/paging/data/GithubRemoteMediator.kt, then compare their apiQuery construction with IN_QUALIFIER in the corresponding GithubService.kt files. Verify that a query such as “Android” produces the documented GitHub search URL and returns repository items in both projects.

Written by the indexing model from the issue text.