Decouple unit test code from business code (#17623)

models/db/main_test.go

@@ -1,14 +0,0 @@
-// Copyright 2021 The Gitea Authors. All rights reserved.
-// Use of this source code is governed by a MIT-style
-// license that can be found in the LICENSE file.
-
-package db
-
-import (
-	"path/filepath"
-	"testing"
-)
-
-func TestMain(m *testing.M) {
-	MainTest(m, filepath.Join("..", ".."))
-}