doc: reorder "releases" entries for reef to fix the diagram

The Gantt diagram currently shows "reef (latest 18.2.0)" instead of
18.2.2.  This is because ReleasesGantt expects releases array to be
sorted in reverse order:

    for code_name, info in releases.items():
        last_release = info['releases'][0]
        first_release = info['releases'][-1]

Signed-off-by: Ilya Dryomov <[email protected]>

Author: idryomov

doc/releases/releases.yml

@@ -15,12 +15,13 @@ releases:
   reef:
     target_eol: 2025-08-01
     releases:
-      - version: 18.2.0
-        released: 2023-08-07
-      - version: 18.2.1
-        released: 2023-12-18
       - version: 18.2.2
         released: 2024-03-11
+      - version: 18.2.1
+        released: 2023-12-18
+      - version: 18.2.0
+        released: 2023-08-07
+
   quincy:
     target_eol: 2024-06-01
     releases: