Documentation/releases: 4.11 isn't "upcoming" anymore.

Change-Id: I7102519b171c3e5269fefaa66d12d605f5d9ddb5
Signed-off-by: Patrick Georgi <pgeorgi@google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/36974
Reviewed-by: HAOUAS Elyes <ehaouas@noos.fr>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

Documentation/releases/coreboot-4.11-relnotes.md

@@ -1,5 +1,5 @@
-Upcoming release - coreboot 4.11
-================================
+coreboot 4.11
+=============
 
 coreboot 4.11 was released on November 19th.