Help: Add "Updates" section header in 3.22 release notes

This was accidentally left out in commit 1461eff899 (Help: Add missing
3.22.1 section to the release notes, 2022-01-24, v3.22.2~1^2).

Help/release/3.22.rst

@@ -143,6 +143,11 @@ Other Changes
 
 * The :cpack_gen:`CPack NSIS Generator` now requires NSIS 3.03 or later.
 
+Updates
+=======
+
+Changes made since CMake 3.22.0 include the following.
+
 3.22.1
 ------