Removed obsolete docs from README.

Author: joachim-n

README.md

@@ -27,11 +27,10 @@ $ composer create-project joachim-n/drupal-core-development-project
 Composer will clone Drupal core into a 'repos/drupal' directory within the
 project, and then symlink that into the project when it installs Drupal core.
 
-Drupal core is checked out to its default branch, which is currently 11.x (see
-limitations below). To start on a different branch without first checking out
-11.x, you can use the `--no-install` option with the `composer create-project`
-command, then change the branch of the Drupal core clone, then do `composer
-install`.
+Drupal core is checked out to its default branch, which is currently 11.x. To
+start on a different branch without first checking out 11.x, you can use the
+`--no-install` option with the `composer create-project` command, then change
+the branch of the Drupal core clone, then do `composer install`.
 
 Once the Composer installation is complete, you can install Drupal as normal,
 either with `drush si` or with the web UI.
@@ -48,12 +47,6 @@ $ ddev composer create joachim-n/drupal-core-development-project
 
 ## Limitations
 
-### Contrib modules on core 11.x branch
-
-Contrib modules can't be installed when Core is checked out to the `11.x`
-branch. For details, see
-https://github.com/joachim-n/drupal-core-development-project/issues/23
-
 ### Contrib and custom tests
 
 Contrib and custom module tests can't be run. For details, see