fix `reserve` in doc
@@ -1315,7 +1315,7 @@ 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.
+ /// Prefer `reserve` if future insertions are expected.
///
/// # Errors
///
