doc: fix year of final LTS release

LTS length was updated to 3 years, but a sentence saying
when the final release would be was not updated.

Fixes: 3c60ea7 ("doc: update LTS maintenance to 3 years")
Cc: [email protected]

Signed-off-by: Kevin Traynor <[email protected]>
Acked-by: Chengwen Feng <[email protected]>

Author: kevintraynor

doc/guides/contributing/stable.rst

@@ -73,7 +73,7 @@ that a tagged release has been tested.
 For a list of the currently maintained stable/LTS branches please see
 the latest `stable roadmap <https://core.dpdk.org/roadmap/#stable>`_.
 
-At the end of the 2 years, a final X.11.N release will be made and at that
+At the end of the 3 years, a final X.11.N release will be made and at that
 point the LTS branch will no longer be maintained with no further releases.