Repository: yt-dlp
Issue: Subtitle download writes to file instead of stdout
Labels: bug,triage

### DO NOT REMOVE OR SKIP THE ISSUE TEMPLATE

- [X] I understand that I will be **blocked** if I *intentionally* remove or skip any mandatory\* field

### Checklist

- [X] I'm reporting a bug unrelated to a specific site
- [X] I've verified that I have **updated yt-dlp to nightly or master** ([update instructions](https://github.com/yt-dlp/yt-dlp#update-channels))
- [X] I've checked that all provided URLs are playable in a browser with the same IP and same login details
- [X] I've checked that all URLs and arguments with special characters are [properly quoted or escaped](https://github.com/yt-dlp/yt-dlp/wiki/FAQ#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 [known issues](https://github.com/yt-dlp/yt-dlp/issues/3766) and 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)

### Provide a description that is worded well enough to be understood

Trying to download subtitles to stdout using `-o -` results in writing to a file with basename `-` instead.

I wanted to pipe and process with other tools such as `sed` in one line. 

```shell
$ yt-dlp --write-auto-sub --skip-download --sub-lang en -o -
[...]
[download] Destination: -.en.vtt
$ rm -- -.en.vtt
```

### Provide verbose output that clearly demonstrates the problem

- [X] Run **your** yt-dlp command with **-vU** flag added (`yt-dlp -vU <your command line>`)
- [ ] If using API, add `'verbose': True` to `YoutubeDL` params instead
- [X] Copy the WHOLE output (starting with `[debug] Command-line config`) and insert it below

### Complete Verbose Output

```shell
[debug] Command-line config: ['-vU', '--write-auto-sub', '--skip-download', '--sub-lang', 'en', '-o', '-', 'https://www.youtube.com/watch?v=-wNyEUrxzFU~']
[debug] Encodings: locale UTF-8, fs utf-8, pref UTF-8, out utf-8, error utf-8, screen utf-8
[debug] yt-dlp version nightly@2024.02.05.232712 from yt-dlp/yt-dlp-nightly-builds [05420227a] (zip)
[debug] Python 3.11.6 (CPython x86_64 64bit) - Linux-6.7.3-arch1-1-x86_64-with-glibc2.38 (OpenSSL 3.2.1 30 Jan 2024, glibc 2.38)
[debug] exe versions: ffmpeg 6.1.1 (setts), ffprobe 6.1.1, rtmpdump 2.4
[debug] Optional libraries: certifi-2023.11.17, requests-2.31.0, sqlite3-3.45.1, urllib3-1.26.18
[debug] Proxy map: {}
[debug] Request Handlers: urllib, requests
[debug] Loaded 1832 extractors
[debug] Fetching release info: https://api.github.com/repos/yt-dlp/yt-dlp-nightly-builds/releases/latest
Latest version: nightly@2024.02.05.232712 from yt-dlp/yt-dlp-nightly-builds
yt-dlp is up to date (nightly@2024.02.05.232712 from yt-dlp/yt-dlp-nightly-builds)
[youtube] Extracting URL: https://www.youtube.com/watch?v=-wNyEUrxzFU~
[youtube] -wNyEUrxzFU: Downloading webpage
[youtube] -wNyEUrxzFU: Downloading ios player API JSON
[youtube] -wNyEUrxzFU: Downloading android player API JSON
[youtube] -wNyEUrxzFU: Downloading m3u8 information
[info] -wNyEUrxzFU: Downloading subtitles: en
[debug] Sort order given by extractor: quality, res, fps, hdr:12, source, vcodec:vp9.2, channels, acodec, lang, proto
[debug] Formats sorted by: hasvid, ie_pref, quality, res, fps, hdr:12(7), source, vcodec:vp9.2(10), channels, acodec, lang, proto, size, br, asr, vext, aext, hasaud, id
[debug] Default format spec: best/bestvideo+bestaudio
[info] -wNyEUrxzFU: Downloading 1 format(s): 18
[info] Writing video subtitles to: -.en.vtt
[debug] Invoking http downloader on "https://www.youtube.com/api/timedtext?v=-wNyEUrxzFU&ei=CcLEZZeFE-qo0u8P2LGGWA&caps=asr&opi=112496729&xoaf=5&hl=en&ip=0.0.0.0&ipbits=0&expire=1707418745&sparams=ip%2Cipbits%2Cexpire%2Cv%2Cei%2Ccaps%2Copi%2Cxoaf&signature=158BEC38BDF2C7F23232E05BD815A7F44B3EC780.C23C5F27DBE279AAD616D8BE472E478444C84EBF&key=yt8&kind=asr&lang=pt&tlang=en&fmt=vtt"
[download] Destination: -.en.vtt
[download] 100% of   29.85KiB in 00:00:00 at 245.66KiB/s
```