remove unused header files #31

Job	Run time
macOS / Release / homebrew-clang	7m 24s
Ubuntu / Release / gcc	21m 30s
macOS / Debug / homebrew-clang	4m 57s
Ubuntu / Debug / gcc	16m 4s
Ubuntu / Release / clang	18m 32s
macOS / Release / system-clang	10m 55s
Ubuntu / Debug / clang	14m 6s
macOS / Debug / system-clang	4m 10s
Windows / Release / cl	28m 25s
Windows / Release / clang	29m 13s
Windows / Release / clang-cl	27m 4s
Windows / Debug / cl	30m 7s
Windows / Debug / clang	18m 11s
Windows / Debug / clang-cl	26m 18s
	4h 16m 56s

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