Validator incorrectly accepts layout=fixed_height

[ithinkihaveacat]

The JS validator at https://validator.amp.dev (incorrectly) considers components with layout fixed_height valid. (This should be written fixed-height.) The validator used in the Google AMP cache does not.

Example doc with layout=fixed_height that is rejected by the Google validator (as expected), but accepted by the JS validator (unexpected): https://brash-grease.glitch.me/

Identical page except with layout=fixed-height for comparison: https://picayune-yttrium.glitch.me/

/cc @Gregable

[honeybadgerdontcare]

This is also true of flex_item, which should be flex-item. It appears the JavaScript engine is changing - in layout to _.