Simplify wording

Co-authored-by: Josh Triplett <[email protected]>
Co-authored-by: Laurențiu Nicola <[email protected]>

library/alloc/src/boxed.rs

@@ -1334,9 +1334,9 @@ impl<T: Copy> From<Cow<'_, [T]>> for Box<[T]> {
     /// Converts a `Cow<'_, [T]>` into a `Box<[T]>`
     ///
     /// When `cow` is the `Cow::Borrowed` variant, this
-    /// conversion allocates on the heap and performs a copy of the
-    /// underlying slice. Otherwise, it will try to re-use the owned
-    /// vec's allocation.
+    /// conversion allocates on the heap and copies the
+    /// underlying slice. Otherwise, it will try to reuse the owned
+    /// `Vec`'s allocation.
     #[inline]
     fn from(cow: Cow<'_, [T]>) -> Box<[T]> {
         match cow {
@@ -1372,7 +1372,7 @@ impl From<Cow<'_, str>> for Box<str> {
     /// Converts a `Cow<'_, str>` into a `Box<str>`
     ///
     /// When `cow` is the `Cow::Borrowed` variant, this
-    /// conversion allocates on the heap and performs a copy of the
+    /// conversion allocates on the heap and copies the
     /// underlying `str`. Otherwise, it will try to re-use the owned
     /// `String`'s allocation.
     ///