Do not overwrite the log mode when installing (#25203) (#25209)

Backport #25203 by @wxiaoguang

Fix #24861

Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

routers/install/install.go

@@ -453,10 +453,9 @@ func SubmitInstall(ctx *context.Context) {
 
 	cfg.Section("session").Key("PROVIDER").SetValue("file")
 
-	cfg.Section("log").Key("MODE").SetValue("console")
+	cfg.Section("log").Key("MODE").MustString("console")
 	cfg.Section("log").Key("LEVEL").SetValue(setting.Log.Level.String())
 	cfg.Section("log").Key("ROOT_PATH").SetValue(form.LogRootPath)
-	cfg.Section("log").Key("ROUTER").SetValue("console")
 
 	cfg.Section("repository.pull-request").Key("DEFAULT_MERGE_STYLE").SetValue("merge")