Remove an unnecessary `let` in spec/features/projects/user_edits_files_spec.rb

It closes #36308

spec/features/projects/user_edits_files_spec.rb

 require 'spec_helper'
 
 describe 'User edits files' do
-  let(:fork_message) do
-    "You're not allowed to make changes to this project directly. "\
-    "A fork of this project has been created that you can make changes in, so you can submit a merge request."
-  end
   let(:project) { create(:project, :repository, name: 'Shop') }
   let(:project2) { create(:project, :repository, name: 'Another Project', path: 'another-project') }
   let(:project_tree_path_root_ref) { project_tree_path(project, project.repository.root_ref) }
@@ -91,7 +87,10 @@ describe 'User edits files' do
 
       click_link('Fork')
 
-      expect(page).to have_content(fork_message)
+      expect(page).to have_content(
+        "You're not allowed to make changes to this project directly. "\
+        "A fork of this project has been created that you can make changes in, so you can submit a merge request."
+      )
 
       execute_script("ace.edit('editor').setValue('*.rbca')")