Update Random_Compat to 2.0.21

[jrf]

Random_Compat 2.0.21 has just been released and by the looks of it, WP is actually quite a bit behind (2.0.11) with the last update of the library having been done in 2017.

Then again, the changes in the interim versions have been minimal and of little consequence for the functionality of the library, save for two Windows specific fixes and improved type safety, which in light of PHP 8.1 is a good thing.

Either way, I'd recommend for the version included with WP to be updated.

Full details:

• ​https://github.com/paragonie/random_compat/releases
• ​https://github.com/paragonie/random_compat/compare/v2.0.11...v2.0.21

I've reviewed the diff and have not found anything which concerns me in it. It should be safe to do this update at the earliest convenience.

Previously: #42439

[SergeyBiryukov]

In 52742:

External Libraries: Update random_compat to version 2.0.21.

The latest release includes improved compatibility with PHP 8.1, as well as some bug fixes for Windows platforms.

Release notes:
​https://github.com/paragonie/random_compat/releases/tag/v2.0.21

For a full list of changes in this update, see the random_compat GitHub:
​https://github.com/paragonie/random_compat/compare/v2.0.11...v2.0.21

Follow-up to [42130].

Props jrf, paragoninitiativeenterprises.
Fixes #55181.

[jrf]

Now this is what I call teamwork - from opening the ticket to commit in 20 minutes flat ;-)

[milana_cap]

Marking for dev note but really needs only mentioning in Field guide.