Merge branch 'update-doc-installation-and-upgrade' into 'master'

Update installation and upgrading guides

[ci skip]

See merge request !10621

doc/install/installation.md

@@ -289,9 +289,9 @@ sudo usermod -aG redis git
 ### Clone the Source
 
     # Clone GitLab repository
-    sudo -u git -H git clone https://gitlab.com/gitlab-org/gitlab-ce.git -b 9-0-stable gitlab
+    sudo -u git -H git clone https://gitlab.com/gitlab-org/gitlab-ce.git -b 9-1-stable gitlab
 
-**Note:** You can change `9-0-stable` to `master` if you want the *bleeding edge* version, but never install master on a production server!
+**Note:** You can change `9-1-stable` to `master` if you want the *bleeding edge* version, but never install master on a production server!
 
 ### Configure It
 

doc/update/9.0-to-9.1.md

 # From 9.0 to 9.1
 
-** TODO: **
-
-# TODO clean out 9.0-specific stuff
-
 Make sure you view this update guide from the tag (version) of GitLab you would
 like to install. In most cases this should be the highest numbered production
 tag (without rc in it). You can select the tag in the version dropdown at the