dev/bisect.sh: fix typo; restore compat with older GAP versions (#5746) #5474

Job	Run time
Cross compiler for s390x	27m 59s
Test in OpenBSD	8m 39s
testinstall - - ubuntu-latest	4m 43s
teststandard - - ubuntu-latest	18m 51s
testmanuals - - ubuntu-latest	6m 17s
testexpect testmockpkg testspecial test-compile testlibgap testkernel testworkspace - - ubuntu-latest	7m 53s
testpackages testinstall-loadall - - ubuntu-latest	26m 12s
makemanuals testmakeinstall - CONFIGFLAGS="--prefix=/tmp/gapprefix" NO_COVERAGE=1 - ubuntu-latest	5m 10s
teststandard - ABI=32 CONFIGFLAGS="" - ubuntu-20.04	18m 10s
testinstall - HPCGAP=yes ABI=64 - ubuntu-latest	7m 11s
testmockpkg testinstall - BOOTSTRAP_MINIMAL=yes - macos-latest	3m 25s
testbugfix - CONFIGFLAGS="--enable-memory-checking" - ubuntu-latest	27m 9s
testbuildsys testmockpkg testinstall - NO_COVERAGE=1 ABI=64 BUILDDIR=out-of-tree CONFIGFLAGS="--enable-valgrind" - ubuntu-latest	5m 25s
testbuildsys testmockpkg testinstall - NO_COVERAGE=1 ABI=32 BUILDDIR=out-of-tree CONFIGFLAGS="" - ubuntu-20.04	3m 42s
testinstall - JULIA=yes CONFIGFLAGS="--enable-debug --disable-Werror" - ubuntu-20.04	4m 31s
testmockpkg testinstall - - windows-2019	15m 13s
Send Slack notification on status change	3s
	3h 10m 33s

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