fix: 修复用户导入模版中没有 password_strategy 字段问题

apps/locale/zh/LC_MESSAGES/django.po

@@ -6486,7 +6486,7 @@ msgstr "是否绑定了虚拟 MFA"
 
 #: users/serializers/user.py:97
 msgid "Can public key authentication"
-msgstr "公钥认证"
+msgstr "可以使用公钥认证"
 
 #: users/serializers/user.py:165
 msgid "Avatar url"

apps/users/serializers/user.py

@@ -81,8 +81,8 @@ class UserSerializer(RolesSerializerMixin, CommonBulkSerializerMixin, serializer
     password_strategy = LabeledChoiceField(
         choices=PasswordStrategy.choices,
         default=PasswordStrategy.email,
+        allow_null=True,
         required=False,
-        write_only=True,
         label=_("Password strategy"),
     )
     mfa_enabled = serializers.BooleanField(read_only=True, label=_("MFA enabled"))