remove unused header files #29

Job	Run time
macOS / Release / homebrew-clang	7m 35s
Ubuntu / Release / gcc	20m 27s
macOS / Debug / homebrew-clang	5m 21s
macOS / Release / system-clang	6m 34s
Ubuntu / Debug / gcc	16m 7s
macOS / Debug / system-clang	4m 47s
Ubuntu / Release / clang	17m 45s
Ubuntu / Debug / clang	13m 34s
Windows / Release / cl	30m 19s
Windows / Release / clang	25m 43s
Windows / Release / clang-cl	25m 20s
Windows / Debug / cl	26m 37s
Windows / Debug / clang	28m 15s
Windows / Debug / clang-cl	20m 52s
	4h 9m 16s

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