fetchers: still retry all other segment's URLs when a non-retryable error happen on the request for one of them
fetchers: still retry all other segment's URLs when a non-retryable error happen on the request for one of them

This fix concerns segment requests for segment with multiple associated
URLs. Due to a misunderstanding of how the `Array.prototype.slice` API
worked, multiple URLs were ignored as soon as one of them failed on an
error that we should not retry.

Basically, we wrote:
```ts
urlsToTry.splice(index);
```
Which means that we should remove every URLs from index.

Where I think we meant:
```ts
urlsToTry.splice(index. 1);
```
Which just does remove the element at `index`.

canalplus/rx-player,canalplus/rx-player,canalplus/rx-player,canalplus/rx-player,canalplus/rx-player