Remove FileSystemFlags dictionary from BCD

[queengooborg]

This PR removes the FileSystemFlags dictionary from BCD.

[ddbeck]

I don't understand the content update. It's not removed. This seems to be a different treatment than we've used in the past. Why?

[queengooborg]

My reasoning for performing a simple unlink of BCD rather than remove the documentation for these pages was because of the number of API members that used the dictionary. In some cases, it makes more sense to keep MDN pages for the dictionary and reference it (for example, CryptoKeyPair) than it is to remove it.

Looking through the MDN pages again, there are only two members using the dictionary, so a simple unlink wasn't the right move. I'll open up a content PR to fix that. However, I think the needs content update can be removed from this PR, since the BCD removal can be done independently now that the table has been unlinked on MDN web docs.