Fixed wording in Rust 1.45 Blog Post (3rd proposal)

Co-authored-by: Niko Matsakis <niko@alum.mit.edu>

Author: JosephTLyons

posts/2020-07-16-Rust-1.45.0.md

@@ -87,7 +87,7 @@ fn main() {
 
 On Rust 1.44.0, this happens to print "x: 0" on my machine. But it could
 print anything, or do anything: this is undefined behavior. But the `unsafe`
-keyword is nowhere to be found within this block of code. This is what we call a
+keyword is not used within this block of code. This is what we call a
 "soundness" bug, that is, it is a bug where the compiler does the wrong thing.
 We tag these bugs as
 [I-unsound](https://github.com/rust-lang/rust/issues?q=is%3Aissue+is%3Aopen+label%3A%22I-unsound+%F0%9F%92%A5%22)