alloc: Use intra doc links for the reserve function

The sentence exists to highlight the existence of a
performance footgun of repeated calls of the
reserve_exact function.

library/alloc/src/collections/vec_deque/mod.rs

@@ -697,7 +697,9 @@ impl<T, A: Allocator> VecDeque<T, A> {
     ///
     /// Note that the allocator may give the collection more space than it
     /// requests. Therefore, capacity can not be relied upon to be precisely
-    /// minimal. Prefer `reserve` if future insertions are expected.
+    /// minimal. Prefer [`reserve`] if future insertions are expected.
+    ///
+    /// [`reserve`]: VecDeque::reserve
     ///
     /// # Errors
     ///

library/alloc/src/string.rs

@@ -1035,7 +1035,9 @@ impl String {
     ///
     /// Note that the allocator may give the collection more space than it
     /// requests. Therefore, capacity can not be relied upon to be precisely
-    /// minimal. Prefer `reserve` if future insertions are expected.
+    /// minimal. Prefer [`reserve`] if future insertions are expected.
+    ///
+    /// [`reserve`]: String::reserve
     ///
     /// # Errors
     ///

library/alloc/src/vec/mod.rs

@@ -811,7 +811,9 @@ impl<T, A: Allocator> Vec<T, A> {
     ///
     /// Note that the allocator may give the collection more space than it
     /// requests. Therefore, capacity can not be relied upon to be precisely
-    /// minimal. Prefer `reserve` if future insertions are expected.
+    /// minimal. Prefer [`reserve`] if future insertions are expected.
+    ///
+    /// [`reserve`]: Vec::reserve
     ///
     /// # Panics
     ///
@@ -875,7 +877,9 @@ impl<T, A: Allocator> Vec<T, A> {
     ///
     /// Note that the allocator may give the collection more space than it
     /// requests. Therefore, capacity can not be relied upon to be precisely
-    /// minimal. Prefer `reserve` if future insertions are expected.
+    /// minimal. Prefer [`reserve`] if future insertions are expected.
+    ///
+    /// [`reserve`]: Vec::reserve
     ///
     /// # Errors
     ///

library/std/src/ffi/os_str.rs

@@ -271,7 +271,9 @@ impl OsString {
     ///
     /// Note that the allocator may give the collection more space than it
     /// requests. Therefore, capacity can not be relied upon to be precisely
-    /// minimal. Prefer reserve if future insertions are expected.
+    /// minimal. Prefer [`reserve`] if future insertions are expected.
+    ///
+    /// [`reserve`]: OsString::reserve
     ///
     /// # Examples
     ///