fix(alerts): Check config to skip incompatible metrics alert (#56383)

Missed a codepath when applying the #56343 fix, this just covers the
same check for the `else` condition

Fixes SENTRY-15Z5

Author: narsaynorath

src/sentry/search/events/builder/metrics.py

@@ -525,7 +525,10 @@ def default_filter_converter(self, search_filter: SearchFilter) -> Optional[Wher
                 value = resolved_value
             else:
                 resolved_item = self.resolve_tag_value(value)
-                if resolved_item is None:
+                if (
+                    resolved_item is None
+                    and not self.builder_config.skip_field_validation_for_entity_subscription_deletion
+                ):
                     raise IncompatibleMetricsQuery(f"{name} value {value} in filter not found")
                 value = resolved_item