Fix dead links in ruby.md

doc/update/ruby.md

 # Updating Ruby from source
 
-This guide explains how to update Ruby in case you installed it from source according to the instructions in https://gitlab.com/gitlab-org/gitlab-ce/blob/masterdoc/install/installation.md#2-ruby .
+This guide explains how to update Ruby in case you installed it from source according to the [instructions](../install/installation.md#2-ruby).
 
 ### 1. Look for Ruby versions
 This guide will only update `/usr/local/bin/ruby`. You can see which Ruby binaries are installed on your system by running:
@@ -36,7 +36,7 @@ sudo gem install bundler
 ```
 
 ### 5. Reinstall GitLab gem bundle
-Just to be sure we will reinstall the gems used by GitLab. Note that the `bundle install` command [depends on your choice of database](https://gitlab.com/gitlab-org/gitlab-ce/blob/masterdoc/install/installation.md#install-gems).
+Just to be sure we will reinstall the gems used by GitLab. Note that the `bundle install` command [depends on your choice of database](../install/installation.md#install-gems).
 
 ```bash
 cd /home/git/gitlab