[CHORE] Move captcha library

- This is a fork of https://github.com/dchest/captcha, as
https://gitea.com/go-chi/captcha is a fork of
github.com/go-macaron/captcha which is a fork (although not properly
credited) of a older version of https://github.com/dchest/captcha. Hence
why I've just forked the original.
- The fork includes some QoL improvements (uses standard library for
determistic RNG instead of rolling your own crypto), and removal of
audio support (500KiB unused data that bloated the binary otherwise).
Flips the image over the x-asis.
47270f2b55..main
- This move is needed for the next commit, because
gitea.com/go-chi/captcha included the gitea.com/go-chi/cache dependency.

go.mod

@@ -5,6 +5,7 @@ go 1.23.0
 require (
 	code.forgejo.org/f3/gof3/v3 v3.7.0
 	code.forgejo.org/forgejo/reply v1.0.2
+	code.forgejo.org/go-chi/captcha v0.0.0-20240827192619-ac88f17cdd8e
 	code.forgejo.org/go-chi/session v0.0.0-20240825010209-bd25d509c8bf
 	code.gitea.io/actions-proto-go v0.4.0
 	code.gitea.io/gitea-vet v0.2.3
@@ -13,7 +14,6 @@ require (
 	connectrpc.com/connect v1.16.2
 	gitea.com/go-chi/binding v0.0.0-20240430071103-39a851e106ed
 	gitea.com/go-chi/cache v0.2.0
-	gitea.com/go-chi/captcha v0.0.0-20240315150714-fb487f629098
 	gitea.com/lunny/levelqueue v0.4.2-0.20230414023320-3c0159fe0fe4
 	github.com/42wim/sshsig v0.0.0-20211121163825-841cf5bbc121
 	github.com/Azure/go-ntlmssp v0.0.0-20221128193559-754e69321358