fix: move filelock import inside function

upgrading users might not be able to run commands because of indirect
import here

frappe/installer.py

@@ -9,7 +9,6 @@
 
 import frappe
 from frappe.defaults import _clear_cache
-from frappe.utils.synchronization import filelock
 
 
 def _new_site(
@@ -427,6 +426,7 @@ def make_site_config(
 
 def update_site_config(key, value, validate=True, site_config_path=None):
 	"""Update a value in site_config"""
+	from frappe.utils.synchronization import filelock
 
 	if not site_config_path:
 		site_config_path = get_site_config_path()