Bug: get_browser_version_from_os return None when use ChromeDriverManager().install()

[CloudX103]

line 161 in webdriver_manager\core\os_manager.py
cmd_mapping = cmd_mapping[browser_type][OperationSystemManager.get_os_name()]

but in #695
(commit 2586bc0)
it removed the @staticmethod Decorator above the get_os_name method

@SergeyPirogov