Updated note on Gemfiles in 10-deployment.md (#9805)

This is a 🔦 documentation change.

I've adjusted the documentation to include a note that Gemfile is
already installed if the reader has completed step 1 in this tutorial. I
thought it was kind of confusing to see instructions on adding a Gemfile
when I had already done that step in the first part of the tutorial.

---------

Co-authored-by: Matt Rogers <mattr-@github.com>

docs/_docs/step-by-step/10-deployment.md

@@ -11,7 +11,7 @@ It's good practice to have a [Gemfile](/docs/ruby-101/#gemfile) for your site.
 This ensures the version of Jekyll and other gems remains consistent across
 different environments.
 
-Create a `Gemfile` in the root. 
+If you completed step one in this tutorial, you have already created a Gemfile. If you skipped step one, create a `Gemfile` in the root. 
 The file should be called 'Gemfile' and should *not* have any extension. 
 You can create a Gemfile with Bundler and then add the `jekyll` gem:
 
@@ -20,7 +20,7 @@ bundle init
 bundle add jekyll
 ```
 
-Your file should look something like:
+Your `Gemfile` should look something like:
 
 ```ruby
 # frozen_string_literal: true