Update ch19-01-unsafe-rust.md

[mirthfulLee]

Original expression Any code that reads or writes from ... should be Any code that reads from or writes to ....
However, compared with access or modify, read from or write to is more tedious but less accurate.
Besides, access or modify also has greater consistency with context : )

[chriskrycho]

Thanks! I understand what you're going for here. However, I think the original is perfectly comprehensible here, and given the overhead of updates to the print book, we are only making changes like this where they are fixing actual bugs or meaningful grammatical mistakes. I think reads or writes from is such a mistake, but let's go with making it just reads from or writes to, rather than making a more general wording change.