Fix ORA-00972 error at test_rename_table_with_prefix_and_suffix

This pull request backports pull request #5837 to 3-2-stable to fix this error.

```ruby
$ ARCONN=oracle ruby -Itest test/cases/migration_test.rb -n 'test_rename_table_with_prefix_and_suffix'
Using oracle with Identity Map off
Run options: -n test_rename_table_with_prefix_and_suffix

# Running tests:

E

Finished tests in 0.184196s, 5.4290 tests/s, 16.2870 assertions/s.

  1) Error:
test_rename_table_with_prefix_and_suffix(MigrationTest):
ArgumentError: New sequence name 'prefix_awesome_things_suffix_seq' is too long; the limit is 30 characters
    /home/yahonda/git/oracle-enhanced/lib/active_record/connection_adapters/oracle_enhanced_schema_statements.rb:105:in `rename_table'
    /home/yahonda/git/rails/activerecord/lib/active_record/migration.rb:466:in `block in method_missing'
    /home/yahonda/git/rails/activerecord/lib/active_record/migration.rb:438:in `block in say_with_time'

1 tests, 3 assertions, 0 failures, 1 errors, 0 skips
$
```

We are going to release new version of Oracle enhanced adapter, I need to test them with the latest 3-2-stable branch.