Change default value of operation parameter of ``QuotaClient.upda…

…te_quota()`` to "="

which is the same of the Galaxy API since 21.09 and makes the
``test_update_non_default_quota`` pass for Galaxy <21.09 without
having to specify the ``operation`` parameter.

bioblend/galaxy/quotas/__init__.py

@@ -142,7 +142,7 @@ def update_quota(
         name: Optional[str] = None,
         description: Optional[str] = None,
         amount: Optional[str] = None,
-        operation: Optional[QuotaOperations] = None,
+        operation: Optional[QuotaOperations] = "=",
         default: Optional[DefaultQuotaValues] = None,
         in_users: Optional[List[str]] = None,
         in_groups: Optional[List[str]] = None,