Remove a few more unnecessary IWYU pragmas #5896

Job	Run time
Test (7.2.1, ubuntu-latest, clang)	36m 12s
Test (7.2.1, windows-latest, msvc)	11m 37s
Test (7.2.1, macos-latest, gcc-14)	8m 22s
Test (7.x, ubuntu-latest, clang)	32m 7s
Test (7.2.1, macos-latest, clang)	11m 2s
Test (7.x, ubuntu-latest, gcc-14)	29m 11s
Test (7.2.1, ubuntu-latest, gcc-14)	25m 29s
Test (7.2.1, windows-latest, clang)	11m 20s
Test (7.x, macos-latest, gcc-14)	8m 0s
Test (7.x, macos-latest, clang)	9m 40s
Test (7.x, windows-latest, clang)	10m 13s
Test (7.x, windows-latest, msvc)	11m 1s
Test (latest, ubuntu-latest, gcc-14)	5m 56s
Test (latest, macos-latest, gcc-14)	7m 8s
Test (latest, ubuntu-latest, clang)	12m 28s
Test (latest, windows-latest, clang)	8m 55s
Test (latest, macos-latest, clang)	11m 25s
Test (latest, windows-latest, msvc)	8m 35s
	4h 18m 41s

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