Maintenance: Remove change-minimizing MemObject::Io hack #235

Job	Run time
CodeQL-tests	28m 17s
functionality-tests	18m 23s
source-maintenance-tests	2m 50s
build-tests(ubuntu-22.04,gcc,default)	5m 33s
build-tests(ubuntu-22.04,gcc,minimal)	4m 59s
build-tests(ubuntu-22.04,gcc,maximus)	6m 7s
build-tests(ubuntu-22.04,clang,default)	6m 33s
build-tests(ubuntu-22.04,clang,minimal)	4m 57s
build-tests(ubuntu-22.04,clang,maximus)	6m 53s
	1h 24m 32s

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