[Google Blockly] Use getGenerator() in all labs

[ajpal]

This was the only change I needed to make in Flappy-specific code.
getGenerator as defined in the CDO Blockly wrapper is

  blocklyWrapper.getGenerator = function() {
    return blocklyWrapper.Generator.get('JavaScript');
  };

Making this a no-op change while we use CDO Blockly.

Doing this everywhere now will allow us to start poking around at other labs with Google Blockly and see what works/what breaks.
For example, I loaded a very simple Maze level and it at least renders correctly:

Links

Testing story

Relying on existing tests

Reviewer Checklist:

• Tests provide adequate coverage
• Privacy and Security impacts have been assessed
• Code is well-commented
• New features are translatable or updates will not break translations
• Relevant documentation has been added or updated
• User impact is well-understood and desirable
• Pull Request is labeled appropriately
• Follow-up work items (including potential tech debt) are tracked and linked