Remove outdated mention of StaticFlags and HsVersions.h from compiler commentary

Jan Hrček reported the following inaccuracies in the Wiki:

I'm reading compiler commentary on GHC wiki and I stumbled upon these 2 out of date pieces, which are currently beyond my knowledge to update them. So just putting it out here.

https://gitlab.haskell.org/ghc/ghc/-/wikis/commentary/compiler/command-line-args mentions Static Flags, but they've been removed in bbd3c399

https://gitlab.haskell.org/ghc/ghc/-/wikis/commentary/coding-style mention HsVersions.h a lot, but it's been removed in 0ef11907

Edited Dec 15, 2021 by Ben Gamari

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