Remove template previewer (#21701)

- Remove "unused" code, I don't think anyone ever used this or was aware
of this feature. It doesn't even work properly as most fields/data are
empty.

routers/web/web.go

@@ -28,7 +28,6 @@ import (
 	"code.gitea.io/gitea/modules/web/routing"
 	"code.gitea.io/gitea/routers/web/admin"
 	"code.gitea.io/gitea/routers/web/auth"
-	"code.gitea.io/gitea/routers/web/dev"
 	"code.gitea.io/gitea/routers/web/events"
 	"code.gitea.io/gitea/routers/web/explore"
 	"code.gitea.io/gitea/routers/web/feed"
@@ -619,10 +618,6 @@ func RegisterRoutes(m *web.Route) {
 
 	m.Post("/{username}", reqSignIn, context_service.UserAssignmentWeb(), user.Action)
 
-	if !setting.IsProd {
-		m.Get("/template/*", dev.TemplatePreview)
-	}
-
 	reqRepoAdmin := context.RequireRepoAdmin()
 	reqRepoCodeWriter := context.RequireRepoWriter(unit.TypeCode)
 	canEnableEditor := context.CanEnableEditor()