Repository: yt-dlp
Issue: [rts.ch]  Unable to extract internal video id
Labels: good first issue,geo-blocked,site-bug,patch-available

### Checklist

- [X] I'm reporting a broken site
- [X] I've verified that I'm running yt-dlp version **2022.02.04**. ([update instructions](https://github.com/yt-dlp/yt-dlp#update))
- [X] I've checked that all provided URLs are alive and playable in a browser
- [X] I've checked that all URLs and arguments with special characters are [properly quoted or escaped](https://github.com/ytdl-org/youtube-dl#video-url-contains-an-ampersand-and-im-getting-some-strange-output-1-2839-or-v-is-not-recognized-as-an-internal-or-external-command)
- [X] I've searched the [bugtracker](https://github.com/yt-dlp/yt-dlp/issues?q=) for similar issues including closed ones. DO NOT post duplicates
- [X] I've read the [guidelines for opening an issue](https://github.com/yt-dlp/yt-dlp/blob/master/CONTRIBUTING.md#opening-an-issue)
- [X] I've read about [sharing account credentials](https://github.com/yt-dlp/yt-dlp/blob/master/CONTRIBUTING.md#are-you-willing-to-share-account-details-if-needed) and I'm willing to share it if required

### Region

Anywhere

### Description

Looks like some regex issue.
Test link:
https://www.rts.ch/info/regions/valais/12865814-un-bouquetin-emporte-par-un-aigle-royal-sur-les-hauts-de-fully-vs.html


### Verbose log

```shell
yt-dlp -v -F https://www.rts.ch/info/regions/valais/12865814-un-bouquetin-emporte-par-un-aigle-royal-sur-les-hauts-de-fully-vs.html
[debug] Command-line config: ['-v', '-F', 'https://www.rts.ch/info/regions/valais/12865814-un-bouquetin-emporte-par-un-aigle-royal-sur-les-hauts-de-fully-vs.html']
[debug] Encodings: locale UTF-8, fs utf-8, out utf-8, err utf-8, pref UTF-8
[debug] yt-dlp version 2022.02.03 [28469edd7] (zip)
[debug] Plugins: ['SamplePluginIE', 'SamplePluginPP']
[debug] Python version 3.9.10 (CPython 64bit) - macOS-11.6.3-arm64-arm-64bit
[debug] exe versions: none
[debug] Optional libraries: sqlite
[debug] Proxy map: {}
[debug] [RTS] Extracting URL: https://www.rts.ch/info/regions/valais/12865814-un-bouquetin-emporte-par-un-aigle-royal-sur-les-hauts-de-fully-vs.html
[RTS] un-bouquetin-emporte-par-un-aigle-royal-sur-les-hauts-de-fully-vs: Downloading JSON metadata
[RTS] un-bouquetin-emporte-par-un-aigle-royal-sur-les-hauts-de-fully-vs: Downloading webpage
ERROR: [RTS] 12865814: Unable to extract internal video id; please report this issue on  https://github.com/yt-dlp/yt-dlp , filling out the "Broken site" issue template properly. Confirm you are on the latest version using -U; please report this issue on  https://github.com/yt-dlp/yt-dlp , filling out the "Broken site" issue template properly. Confirm you are on the latest version using -U
  File "/Users/zig/Downloads/DrB/yt-dlp/./yt-dlp/yt_dlp/extractor/common.py", line 615, in extract
    ie_result = self._real_extract(url)
  File "/Users/zig/Downloads/DrB/yt-dlp/./yt-dlp/yt_dlp/extractor/rts.py", line 159, in _real_extract
    internal_id = self._html_search_regex(
  File "/Users/zig/Downloads/DrB/yt-dlp/./yt-dlp/yt_dlp/extractor/common.py", line 1198, in _html_search_regex
    res = self._search_regex(pattern, string, name, default, fatal, flags, group)
  File "/Users/zig/Downloads/DrB/yt-dlp/./yt-dlp/yt_dlp/extractor/common.py", line 1189, in _search_regex
    raise RegexNotFoundError('Unable to extract %s' % _name)
```