Clarify that you are install bundler, and bundler takes care of jekyll (#6286)

Signed-off-by: Eric Pugh <epugh@opensourceconnections.com>

CONTRIBUTING.md

@@ -86,13 +86,13 @@ Follow these steps to set up your local copy of the repository:
    ruby -v
    ```
 
-1. Install [Jekyll](https://jekyllrb.com/) if you don't already have it:
+1. Install [Bundler](https://bundler.io/) if you don't already have it:
 
    ```
-   gem install bundler jekyll
+   gem install bundler
    ```
 
-1. Install the Jekyll dependencies:
+1. Install Jekyll and all the dependencies:
 
    ```
    bundle install