Reword the section on union assignments

Author: cuviper

posts/2021-02-11-Rust-1.50.0.md

@@ -54,12 +54,12 @@ fn main() {
 
 ### Safe assignments to `ManuallyDrop<T>` union fields
 
-Rust 1.49 made it possible to add `ManuallyDrop<T>` fields to a `union`
-as part of allowing `Drop` for unions at all; however, unions don't know
-which variant is valid (they don't drop any old value on assignment), so
-safe Rust has limited this to `Copy` types only, which never `Drop`. Of
-course, that's also true of `ManuallyDrop`, so now Rust 1.50 allows safe
-assignments to these fields as well.
+Rust 1.49 made it possible to add `ManuallyDrop<T>` fields to a `union` as part
+of allowing `Drop` for unions at all. However, unions don't drop old values
+when a field is assigned, since they don't know which variant was formerly
+valid, so safe Rust has limited this to `Copy` types only, which never `Drop`.
+Of course, `ManuallyDrop<T>` also doesn't need to `Drop`, so now Rust 1.50
+allows safe assignments to these fields as well.
 
 ### A niche for `File` on Unix platforms