many items on the feature matureness page are duped in the table

[bmillsNV]

many items on the feature matureness page are duped in the table https://shader-slang.org/docs/feature_matureness/ - see: Generic existential types, Multi-file Modules (__include), Non-generic existential types (static dispatch), etc.

[bmillsNV]

@csyonghe looks like you updated this page last. can you fix it? Please ensure it's reviewed properly.