fix locale warning

DeprecationWarning: 'locale.getdefaultlocale' is deprecated and slated for removal in Python 3.15. Use setlocale(), getencoding() and getlocale() instead.
rewrite using getlocale

Author: Stepan Neretin

testgres/operations/os_ops.py

@@ -20,7 +20,8 @@ def __init__(self, host='127.0.0.1', port=None, ssh_key=None, username=None):
 
 
 def get_default_encoding():
-    return locale.getdefaultlocale()[1] or 'UTF-8'
+    locale.setlocale(locale.LC_ALL, '')
+    return locale.getencoding() or 'UTF-8'
 
 
 class OsOperations: