doc-bot: update form letter for 6.10

Signed-off-by: Jakub Kicinski <[email protected]>

Author: kuba-moo

form-letters/net-next-closed

@@ -1,8 +1,8 @@
-The merge window for v6.9 has begun and we have already posted our pull
+The merge window for v6.10 has begun and we have already posted our pull
 request. Therefore net-next is closed for new drivers, features, code
 refactoring and optimizations. We are currently accepting bug fixes only.
 
-Please repost when net-next reopens after March 25th.
+Please repost when net-next reopens after May 26th.
 
 RFC patches sent for review only are obviously welcome at any time.