Upgrade gitea to 1.20.2 from 1.18.4

[robe]

I never got around to upgrading prod to 1.19. Now 1.20.2 is out.

I'll refresh dev first and upgrade it to see how it goes.

Key features of 1.20 that might be useful to us ​https://github.com/go-gitea/gitea/releases/tag/v1.20.0

• Add Go package registry (#24687)
• Add Debian package registry (#24426) - might be useful if we want to provide indevelop binaries to our Debian/Debian fork users I haven't looked what's involved, but perhaps woodie or dronie can serve to build scheduled packages
• Add RPM registry (#23380) (ditto as Debian but for our RPM users)
• Add CRAN package registry (#22331) (for some of our R indevelopment, I think we have some projects that need to publish there)
• Add the ability to pin Issues (#24406)
• Allow webp images as avatars (#24248)
• There is work in progress going on to implement github actions style stuff

One is Implement actions artifacts (#22738)

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I tested on dev and seems fine

​https://github.com/go-gitea/gitea/releases/tag/v1.19.0

Lots of new features, main one at least strk is excited about is:

Add support for incoming emails ​https://github.com/go-gitea/gitea/pull/22056

though I presume that means we need to setup some IMAP mailbox thingy for it to receive.

Other possibly useful stuff in v1.19

• Add Conda package registry (I didn't realize conda can be used for more than python packages and you can host your own)
• Add Cargo package registry (since rust is getting more popular, might be useful)
• Support scoped access tokens
• Secrets storage with SecretKey encrypted (​https://github.com/go-gitea/gitea/pull/22142)

[strk]

See also #2921 :)