Disable Platform text-recognition functionality

Mozilla's text recognition API is currently macOS only and calls out to these platfoms apis: https://developer.apple.com/documentation/vision/recognizing_text_in_images

In the future this could/should be replaced with local in-process OCR system like teseract ( https://github.com/tesseract-ocr/tesseract ). For now let's neuter the global check to hard return false always and prevent all the dependent code paths from being taken.