system: change System class to a dvc.fs.system module

tests/func/test_remove.py

@@ -4,7 +4,7 @@ import pytest
 
 from dvc.cli import main
 from dvc.exceptions import DvcException
-from dvc.fs.system import System
+from dvc.fs import system
 from dvc.stage.exceptions import StageFileDoesNotExistError
 from dvc.utils.fs import remove
 from tests.utils import get_gitignore_content
@@ -45,7 +45,7 @@ def test_remove_broken_symlink(tmp_dir, dvc):
 
     (stage,) = dvc.add("foo")
     remove(dvc.odb.local.cache_dir)
-    assert System.is_symlink("foo")
+    assert system.is_symlink("foo")
 
     with pytest.raises(DvcException):
         dvc.remove(stage.addressing)