Suppress a RuboCop's offense

This commit suppresses the following RuboCop's offense:

```console
$ bundle exec rake
(snip)
lib/rubocop/rails/schema_loader/schema.rb:181:11: C: [Corrected] Style/SuperArguments:
Call super without arguments and parentheses when the signature is identical.
          super(node)
          ^^^^^^^^^^^

294 files inspected, 1 offense detected, 1 offense corrected
```

lib/rubocop/rails/schema_loader/schema.rb

@@ -178,7 +178,7 @@ class AddIndex < Index
         attr_reader :table_name
 
         def initialize(node)
-          super(node)
+          super
 
           @table_name = node.first_argument.value
           @columns, @expression = build_columns_or_expr(node.arguments[1])