Update comment

Author: erindru

sqlmesh/core/plan/explainer.py

@@ -271,7 +271,8 @@ def visit_restatement_stage(
 
                     for snapshot, clear_request in requests:
                         if not snapshot:
-                            # Snapshots are None (not loaded) unless
+                            # This check is mostly for mypy, snapshots should have been loaded
+                            # while creating the ExplainableRestatementStage if the verbosity was set to VERY_VERBOSE
                             continue
                         if clear_request.sorted_environment_names:
                             # snapshot is promoted in these environments