Do not lint migrations on dry_run

If the migration file is not generated, we're not able yet to generate the associated SQL.
That'll come in a later version :)

django_migration_linter/management/commands/makemigrations.py

@@ -30,11 +30,14 @@ class Command(MakeMigrationsCommand):
 
     def write_migration_files(self, changes):
         super(Command, self).write_migration_files(changes)
+
         if (
             not getattr(settings, "MIGRATION_LINTER_OVERRIDE_MAKEMIGRATIONS", False)
             and not self.lint
         ):
             return
+        if self.dry_run:
+            return
 
         # Lint migrations
         linter = MigrationLinter(