remove invalid resource types from the metadata

We have seen several mlses list a Resource type in the metadata, but
then never reference in the list of classes. This breaks our
metadata, as we assumed all resources had a class. This fixes that
potential bug.
Adding this field breaks `Oj.dump`. We dump and cache metadata in json. Code to demonstrate the problem:

```
DEVELOPMENT [1] pry(main)> class Cls ; def initialize ; @logger = Logger.new STDOUT; end ; end
=> :initialize
DEVELOPMENT [2] pry(main)> c = Cls.new
=> #<Cls:0x000001083dc698
 @logger=
  #<Logger:0x000001083dc670
   @default_formatter=
    #<Logger::Formatter:0x000001083dc620 @datetime_format=nil>,
   @formatter=nil,
   @level=0,
   @logdev=
    #<Logger::LogDevice:0x000001083dc5a8
     @dev=#<IO:<STDOUT>>,
     @filename=nil,
     @mutex=
      #<Logger::LogDevice::LogDeviceMutex:0x000001083dc580
       @mon_count=0,
       @mon_mutex=#<Mutex:0x000001083dc530>,
       @mon_owner=nil>,
     @shift_age=nil,
     @shift_size=nil>,
   @progname=nil>>
DEVELOPMENT [3] pry(main)> Oj.dump(c)
NotImplementedError: Failed to dump 'IO' Object (0b)
from (pry):3:in `dump'
```