Fix typo: necessary -> necessarily

Author: elkowar

_posts/2021-07-09-inline-in-rust.adoc

@@ -3,7 +3,7 @@
 There's a lot of tribal knowledge surrounding https://doc.rust-lang.org/reference/attributes/codegen.html#the-inline-attribute[`++#[inline]++`] attribute in Rust.
 I often find myself teaching how it works, so I finally decided to write this down.
 
-Caveat Emptor: this is what I know, not necessary what is true.
+Caveat Emptor: this is what I know, not necessarily what is true.
 Additionally, exact semantics of `+#[inline]+` is not set in stone and may change in future Rust versions.
 
 == Why Inlining Matters?