Fix typo in 1.20.0 release notes
Fix typo in 1.20.0 release notes

str::from_boxed_utf8_unchecked rather than ste::
GBGamer/rust,graydon/rust,GBGamer/rust,aidancully/rust,graydon/rust,aidancully/rust,GBGamer/rust,graydon/rust,aidancully/rust,GBGamer/rust,graydon/rust,GBGamer/rust,GBGamer/rust,graydon/rust,aidancully/rust,graydon/rust,GBGamer/rust,aidancully/rust,GBGamer/rust,aidancully/rust