Use Go 1.20 for next release (#24859)

Author: wxiaoguang

docs/config.yaml

@@ -18,8 +18,8 @@ params:
   description: Git with a cup of tea
   author: The Gitea Authors
   website: https://docs.gitea.io
-  version: 1.19.0
-  minGoVersion: 1.19
+  version: 1.19.0 # FIXME: this version was used as "latest stable release", but it always gets outdated and doesn't make sense
+  minGoVersion: 1.20
   goVersion: 1.20
   minNodeVersion: 16
   search: nav

go.mod

@@ -1,6 +1,6 @@
 module code.gitea.io/gitea
 
-go 1.19
+go 1.20
 
 require (
 	code.gitea.io/actions-proto-go v0.2.1