unified_strdate returns None on dates with "3rd" and "23rd"

[InfernalUnderling]

Checklist

• I'm reporting a broken site support issue
• I've verified that I'm running youtube-dl version 2019.11.22
• I've checked that all provided URLs are alive and playable in a browser
• I've checked that all URLs and arguments with special characters are properly quoted or escaped
• I've searched the bugtracker for similar bug reports including closed ones
• I've read bugs section in FAQ

Verbose log

[debug] System config: []
[debug] User config: []
[debug] Custom config: []
[debug] Command-line args: ['https://www.bitchute.com/video/KDAtOH7nEUGe/', '--no-check-certificate', '--verbose']
[debug] Encodings: locale UTF-8, fs utf-8, out UTF-8, pref UTF-8
[debug] youtube-dl version 2019.11.22
[debug] Git HEAD: 8267f2f
[debug] Python version 3.7.4 (CPython) - Linux-5.3.8-gnu-x86_64-with-glibc2.2.5
[debug] exe versions: ffmpeg 4.2.1, ffprobe 4.2.1
[debug] Proxy map: {}
[BitChute] KDAtOH7nEUGe: Downloading webpage
[BitChute] KDAtOH7nEUGe: Checking video URL

(Custom output snipped. See description for details.)

Description

"unified_strdate" from utils returns None instead of a date if the string sent contains "3rd" or "23rd".

I initially discovered this issue when creating pull #23193. Other sites (such as youtube) don't seem to have prefixes such as "*st", "*nd", "*rd", etc, on the day of the month, and thus don't seem to run into this problem when getting dates.

I hacked together a quick test patch that runs through all possible dates and displays them along with the converted version from unified_strdate. The full output and the test patch are attached. To run it, just apply the patch and tell youtube-dl to download any bitchute video (I used "https://www.bitchute.com/video/KDAtOH7nEUGe/" in this example, but any video will work).

date_test_patch.txt
output.txt

As you can see from this snippet, all of the 3rd and 23rd days return "None" instead of a date. The full output also has "None" in days that do not exist (such as February 31st), since this was just a quick hack to check which dates worked and which didn't.

January 1st, 2019:  20190101
January 2nd, 2019:  20190102
January 3rd, 2019:  None
January 4th, 2019:  20190104
...
January 22nd, 2019:  20190122
January 23rd, 2019:  None
January 24th, 2019:  20190124
...
February 2nd, 2019:  20190202
February 3rd, 2019:  None
February 4th, 2019:  20190204
...