feat(index): update user index staging flag

Set the staging flag to True for the "user" index in the index.py file.

tracardi/service/storage/index.py

@@ -261,7 +261,7 @@ def __init__(self):
                                       partitioning=tracardi.field_change_log_partitioning,
                                       index="tracardi-field-update-log",
                                       mapping="mappings/field-update-log-index.json"),
-            "user": Index(staging=False,
+            "user": Index(staging=True,
                           multi_index=False,
                           index="tracardi-user",
                           mapping="mappings/user-index.json"),