Don't add classes to the top level namespace

I've been writing too much Rust. My mind is still in the mode of things
being auto-namespaced based on the file...

activerecord/lib/active_record/connection_adapters/determine_if_preparable_visitor.rb

@@ -1,4 +1,6 @@
-module DetermineIfPreparableVisitor
+module ActiveRecord
+  module ConnectionAdapters
+    module DetermineIfPreparableVisitor
       attr_reader :preparable
 
       def accept(*)
@@ -15,4 +17,6 @@ def visit_Arel_Nodes_SqlLiteral(*)
         @preparable = false
         super
       end
+    end
+  end
 end