Remove unused sparselist code #5826

Job	Run time
Cross compiler for s390x	27m 6s
Test in OpenBSD	7m 47s
testinstall - - ubuntu-latest	4m 37s
teststandard - - ubuntu-latest	19m 24s
testmanuals - - ubuntu-latest	6m 0s
testexpect testmockpkg testspecial test-compile testlibgap testkernel testworkspace - - ubuntu-latest	6m 28s
testpackages testinstall-loadall - - ubuntu-latest	26m 0s
makemanuals testmakeinstall - CONFIGFLAGS="--prefix=/tmp/gapprefix" NO_COVERAGE=1 - ubuntu-latest	5m 28s
teststandard - ABI=32 CONFIGFLAGS="" - ubuntu-20.04	18m 40s
testinstall - HPCGAP=yes ABI=64 - ubuntu-latest	8m 12s
testmockpkg testinstall - BOOTSTRAP_MINIMAL=yes - macos-latest	4m 1s
testbugfix - CONFIGFLAGS="--enable-memory-checking" - ubuntu-latest	29m 21s
testbuildsys testmockpkg testinstall - NO_COVERAGE=1 ABI=64 BUILDDIR=out-of-tree CONFIGFLAGS="--enable-valgrind" - ubuntu-latest	4m 27s
testbuildsys testmockpkg testinstall - NO_COVERAGE=1 ABI=32 BUILDDIR=out-of-tree CONFIGFLAGS="" - ubuntu-20.04	4m 19s
testinstall - JULIA=yes CONFIGFLAGS="--enable-debug" - ubuntu-20.04	4m 32s
testmockpkg testinstall - - windows-2019	14m 51s
Send Slack notification on status change	0s
	3h 11m 13s

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