Maintenance: Remove change-minimizing MemObject::Io hack #232

Job	Run time
functionality-tests	1m 12s
CodeQL-tests	3m 37s
source-maintenance-tests	2m 58s
build-tests(ubuntu-22.04,gcc,default)	2m 20s
build-tests(ubuntu-22.04,gcc,minimal)	2m 4s
build-tests(ubuntu-22.04,gcc,maximus)	2m 21s
build-tests(ubuntu-22.04,clang,default)	2m 19s
build-tests(ubuntu-22.04,clang,minimal)	2m 26s
build-tests(ubuntu-22.04,clang,maximus)	2m 20s
	21m 37s

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