make writing main test easier (#27270)

This PR removed `unittest.MainTest` the second parameter
`TestOptions.GiteaRoot`. Now it detects the root directory by current
working directory.

---------

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

models/main_test.go

@@ -29,7 +29,5 @@ func TestFixturesAreConsistent(t *testing.T) {
 }
 
 func TestMain(m *testing.M) {
-	unittest.MainTest(m, &unittest.TestOptions{
-		GiteaRootPath: "..",
-	})
+	unittest.MainTest(m)
 }