fix the whatis lines in scheme.1.in #304

Job	Run time
ci (tpb, ubuntu-22.04, --pb --threads --enable-libffi, test-some-fast)	28m 30s
ci (a6osx, macos-12)	13m 53s
ci (ta6osx, macos-12)	18m 55s
ci (arm64osx, macos-14)	8m 15s
ci (tarm64osx, macos-14)	10m 12s
ci (i3le, ubuntu-22.04)	11m 20s
ci (ti3le, ubuntu-22.04)	14m 19s
ci (a6le, ubuntu-22.04)	8m 56s
ci (ta6le, ubuntu-22.04, CFLAGS+=-std=gnu89)	11m 41s
ci (ta6le, ubuntu-22.04, reboot, -m=ta6le --force, re.boot SCHEME="chezscheme", test-some-fast)	8m 1s
ci (i3nt, windows-2022, vs)	11m 46s
ci (ti3nt, windows-2022, vs)	14m 48s
ci (a6nt, windows-2022, vs)	11m 51s
ci (ta6nt, windows-2022, vs)	15m 6s
ci (ta6nt, windows-2022, gcc, CFLAGS+=-std=gnu89)	13m 44s
	3h 21m 17s

Provide feedback