remove unused header files #33

Job	Run time
macOS / Release / homebrew-clang	7m 15s
Ubuntu / Release / gcc	22m 41s
macOS / Debug / homebrew-clang	6m 28s
Ubuntu / Debug / gcc	17m 56s
macOS / Release / system-clang	5m 31s
Ubuntu / Release / clang	17m 54s
macOS / Debug / system-clang	4m 37s
Ubuntu / Debug / clang	15m 26s
Windows / Release / cl	30m 43s
Windows / Release / clang	31m 20s
Windows / Release / clang-cl	24m 48s
Windows / Debug / cl	25m 16s
Windows / Debug / clang	24m 55s
Windows / Debug / clang-cl	15m 34s
	4h 10m 24s

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