fix indentation when printing double cosets (#5841) #5880

Job	Run time
Test in OpenBSD	7m 51s
Cross compiler for s390x	28m 13s
testinstall - - ubuntu-latest	4m 56s
teststandard - - ubuntu-latest	20m 0s
testmanuals - - ubuntu-latest	6m 3s
testexpect testmockpkg testspecial test-compile testlibgap testkernel testworkspace - - ubuntu-latest	6m 57s
testpackages testinstall-loadall - - ubuntu-latest	26m 19s
makemanuals testmakeinstall - CONFIGFLAGS="--prefix=/tmp/gapprefix" NO_COVERAGE=1 - ubuntu-latest	5m 16s
teststandard - ABI=32 CONFIGFLAGS="" - ubuntu-20.04	18m 10s
testinstall - HPCGAP=yes ABI=64 - ubuntu-latest	7m 33s
testmockpkg testinstall - BOOTSTRAP_MINIMAL=yes - macos-latest	4m 10s
testbugfix - CONFIGFLAGS="--enable-memory-checking" - ubuntu-latest	29m 59s
testbuildsys testmockpkg testinstall - NO_COVERAGE=1 ABI=64 BUILDDIR=out-of-tree CONFIGFLAGS="--enable-valgrind" - ubuntu-latest	4m 28s
testbuildsys testmockpkg testinstall - NO_COVERAGE=1 ABI=32 BUILDDIR=out-of-tree CONFIGFLAGS="" - ubuntu-20.04	4m 4s
testinstall - JULIA=yes CONFIGFLAGS="--enable-debug" - ubuntu-20.04	4m 35s
testmockpkg testinstall - - windows-2019	15m 32s
Send Slack notification on status change	3s
	3h 14m 9s

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