Get rid of duplicated @quoted_table_name cache

Since rails#23658 `quote_table_name` returns cached value for all adapters.

Author: kamipo

activerecord/lib/active_record/model_schema.rb

@@ -276,15 +276,14 @@ def table_name=(value)
         end
 
         @table_name        = value
-        @quoted_table_name = nil
         @arel_table        = nil
         @sequence_name     = nil unless @explicit_sequence_name
         @predicate_builder = nil
       end
 
       # Returns a quoted version of the table name, used to construct SQL statements.
       def quoted_table_name
-        @quoted_table_name ||= adapter_class.quote_table_name(table_name)
+        adapter_class.quote_table_name(table_name)
       end
 
       # Computes the table name, (re)sets it internally, and returns it.