[libcxx] Fix a typo in documentation

[kazutakahirata]

No description provided.

[llvmbot]

@llvm/pr-subscribers-libcxx

Author: Kazu Hirata (kazutakahirata)

Changes

---

Full diff: https://github.com/llvm/llvm-project/pull/148557.diff

1 Files Affected:

• (modified) libcxx/docs/ReleaseNotes/21.rst (+1-1)

diff --git a/libcxx/docs/ReleaseNotes/21.rst b/libcxx/docs/ReleaseNotes/21.rst
index 3d70fa38d971e..96115890e5520 100644
--- a/libcxx/docs/ReleaseNotes/21.rst
+++ b/libcxx/docs/ReleaseNotes/21.rst
@@ -85,7 +85,7 @@ Improvements and New Features
 - The ``flat_map::insert`` and ``flat_set::insert_range`` have been optimized, resulting in a performance improvement of up
   to 10x for inserting elements into a ``flat_map`` when the input range is a ``flat_map`` or a ``zip_view``.
 
-- ``ctype::tolower`` and ``ctype::toupper`` have been optimized, resulting in a 2x performane improvement.
+- ``ctype::tolower`` and ``ctype::toupper`` have been optimized, resulting in a 2x performance improvement.
 
 Deprecations and Removals
 -------------------------