fix(deletes): some ch versions dont have setting (#7536)

FIXES
[SNUBA-9X1](https://sentry.sentry.io/issues/7025379706/?project=300688&referrer=github-pr-bot)

Although this wont be an issue once all the clusters are upgraded
getsentry/ops#17973

Author: MeredithAnya

snuba/lw_deletions/strategy.py

@@ -98,8 +98,10 @@ def _execute_delete(self, conditions: Sequence[ConditionsType]) -> None:
         self._check_ongoing_mutations()
         query_settings = HTTPQuerySettings()
         # starting in 24.4 the default is 2
-        lw_sync = get_int_config("lightweight_deletes_sync", 2)
-        query_settings.set_clickhouse_settings({"lightweight_deletes_sync": lw_sync})
+        lw_sync = get_int_config("lightweight_deletes_sync")
+        if lw_sync is not None:
+            query_settings.set_clickhouse_settings({"lightweight_deletes_sync": lw_sync})
+
         for table in self.__tables:
             query = construct_query(self.__storage, table, construct_or_conditions(conditions))
             start = time.time()

tests/lw_deletions/test_lw_deletions.py

@@ -96,6 +96,7 @@ def test_clickhouse_settings(mock_execute: Mock, mock_num_mutations: Mock) -> No
         next_step=FormatQuery(commit_step, storage, SearchIssuesFormatter(), metrics),
         increment_by=increment_by,
     )
+    state.set_config("lightweight_deletes_sync", 2)
     make_message = generate_message()
     strategy.submit(next(make_message))
     strategy.submit(next(make_message))