Fixed broken link

docs/book/src/reference/completion.md

@@ -5,7 +5,7 @@ Note that sourcing the completion script in your shell enables Kubebuilder autoc
 </aside>
 <aside class="note">
 <h1>Prerequisites for Bash</h1>
-The completion Bash script depends on [bash-completion](https://github.com/scop/bash-completion), which means that you have to install this software first (you can test if you have bash-completion already installed. Also, ensure that your Bash version is 4.1+. 
+The completion Bash script depends on [bash-completion][bash-completion], which means that you have to install this software first (you can test if you have bash-completion already installed). Also, ensure that your Bash version is 4.1+. 
 </aside>
 
 
@@ -29,3 +29,5 @@ fi
 - Restart terminal for the changes to be reflected.
 
 Follow a similar protocol for `zsh` completion.
+
+[bash-completion]: https://github.com/scop/bash-completion