Merge branch 'yatish27/gitlab-ce-project-commit-range-comment' into 'master'

Fix comment for project argument in commit_range.rb

## What does this MR do?
It fixes the documentation for commit_range project argument

## Are there points in the code the reviewer needs to double check?

## Why was this MR needed?

## What are the relevant issue numbers?

## Screenshots (if relevant)

## Does this MR meet the acceptance criteria?

- [ ] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added
- [ ] [Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)
- [ ] API support added
- [ ] Tests
  - [ ] Added for this feature/bug
  - [ ] All builds are passing
- [ ] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [ ] Branch has no merge conflicts with `master` (if you do - rebase it please)
- [ ] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

See merge request !4805

app/models/commit_range.rb

@@ -23,7 +23,7 @@ class CommitRange
   attr_reader :commit_from, :notation, :commit_to
   attr_reader :ref_from, :ref_to
 
-  # Optional Project model
+  # The Project model
   attr_accessor :project
 
   # The beginning and ending refs can be named or SHAs, and
@@ -56,7 +56,7 @@ class CommitRange
   # Initialize a CommitRange
   #
   # range_string - The String commit range.
-  # project      - An optional Project model.
+  # project      - The Project model.
   #
   # Raises ArgumentError if `range_string` does not match `PATTERN`.
   def initialize(range_string, project)