simplify the code for `IsObjWithMemory` #5993

Job	Run time
Cross compiler for s390x	27m 31s
Test in OpenBSD	8m 3s
testinstall - - ubuntu-latest	4m 36s
teststandard - - ubuntu-latest	19m 29s
testmanuals - - ubuntu-latest	5m 56s
testexpect testmockpkg testspecial test-compile testlibgap testkernel testworkspace - - ubuntu-latest	6m 39s
testpackages testinstall-loadall - - ubuntu-latest	26m 14s
makemanuals testmakeinstall - CONFIGFLAGS="--prefix=/tmp/gapprefix" NO_COVERAGE=1 - ubuntu-latest	6m 54s
teststandard - ABI=32 CONFIGFLAGS="" - ubuntu-20.04	18m 16s
testinstall - HPCGAP=yes ABI=64 - ubuntu-latest	7m 16s
testmockpkg testinstall - BOOTSTRAP_MINIMAL=yes - macos-latest	4m 12s
testbugfix - CONFIGFLAGS="--enable-memory-checking" - ubuntu-latest	29m 44s
testbuildsys testmockpkg testinstall - NO_COVERAGE=1 ABI=64 BUILDDIR=out-of-tree CONFIGFLAGS="--enable-valgrind" - ubuntu-latest	4m 24s
testbuildsys testmockpkg testinstall - NO_COVERAGE=1 ABI=32 BUILDDIR=out-of-tree CONFIGFLAGS="" - ubuntu-20.04	4m 12s
testinstall - JULIA=yes CONFIGFLAGS="--enable-debug" - ubuntu-20.04	4m 36s
testmockpkg testinstall - - windows-2019	15m 32s
Send Slack notification on status change	0s
	3h 13m 34s

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