Rollup merge of #40603 - QuietMisdreavus:slice-ptr-docs, r=GuillaumeGomez

minor wording tweak to slice::{as_ptr, as_mut_ptr}

Per #37334, the slice-as-pointer methods mentioned that "modifying the slice may cause its buffer to be reallocated", when in fact modifying the *slice* itself would cause no such change. (It is a borrow, after all!) This is a tweak to the wording of that line to stress it's the *collection* that could cause the buffer to be reallocated.

r? @steveklabnik

Author: frewsxcv

src/libcollections/slice.rs

@@ -437,8 +437,8 @@ impl<T> [T] {
     /// The caller must ensure that the slice outlives the pointer this
     /// function returns, or else it will end up pointing to garbage.
     ///
-    /// Modifying the slice may cause its buffer to be reallocated, which
-    /// would also make any pointers to it invalid.
+    /// Modifying the container referenced by this slice may cause its buffer
+    /// to be reallocated, which would also make any pointers to it invalid.
     ///
     /// # Examples
     ///
@@ -463,8 +463,8 @@ impl<T> [T] {
     /// The caller must ensure that the slice outlives the pointer this
     /// function returns, or else it will end up pointing to garbage.
     ///
-    /// Modifying the slice may cause its buffer to be reallocated, which
-    /// would also make any pointers to it invalid.
+    /// Modifying the container referenced by this slice may cause its buffer
+    /// to be reallocated, which would also make any pointers to it invalid.
     ///
     /// # Examples
     ///