Correct upgrade guides for 12.0

It's fine to upgrade from 11.11.x to 12.x, so we remove the requirement
to first upgrade to 12.0.x.

doc/update/upgrading_from_source.md

@@ -412,18 +412,15 @@ Additional instructions here.
 
 In 12.0.0 we made various database related changes. These changes require that
 users first upgrade to the latest 11.11 patch release. Once upgraded to 11.11.x,
-users can upgrade to 12.0.x. You **can not** upgrade from 11.11.x to 12.1.0 or a
-newer version, instead you **must** first upgrade to 12.0.0. Failure to do so
-may result in database migrations not being applied, which could lead to
-application errors.
+users can upgrade to 12.x. Failure to do so may result in database migrations
+not being applied, which could lead to application errors.
 
 Example 1: you are currently using GitLab 11.11.3, which is the latest patch
-release for 11.11.x. To upgrade, first upgrade to 12.0.0, then upgrade to any
-future versions.
+release for 11.11.x. You can upgrade as usual to 12.0.0, 12.1.0, etc.
 
 Example 2: you are currently using a version of GitLab 10.x. To upgrade, first
-upgrade to 11.11.3. Once upgraded to 11.11.3 you can safely upgrade to 12.0.0,
-then upgrade to any future versions.
+upgrade to 11.11.3. Once upgraded to 11.11.3 you can safely upgrade to 12.0.0
+or future versions.
 
 ## Things went south? Revert to previous version