doc: invert sentence on setattr logic in NG #672

Job	Run time
Build docs & run doctests	29s
Check types using pyright	36s
Verify dev env (ubuntu-latest)	28s
Tests & Mypy on 3.7	2m 15s
Verify dev env (windows-latest)	1m 5s
Tests & Mypy on 3.8	1m 20s
Tests & Mypy on 3.9	1m 22s
Tests & Mypy on 3.10	1m 33s
Tests & Mypy on 3.11	2m 3s
Tests & Mypy on 3.12	1m 40s
Tests & Mypy on pypy-3.8	1m 41s
Tests & Mypy on pypy-3.9	1m 13s
Tests & Mypy on pypy-3.10	1m 22s
Combine & check coverage.	11s
required-checks-pass	8s
	17m 26s

Provide feedback