Fix solidus frontend branch name

Solidus frontend doesn't have newer versions so specifying the branch
for new versions won't work. If the branch is too high it will just
error because it doesn't exist.

Author: AlistairNorman

Gemfile

@@ -4,13 +4,18 @@ source 'https://rubygems.org'
 git_source(:github) { |repo| "https://github.com/#{repo}.git" }
 
 branch = ENV.fetch('SOLIDUS_BRANCH', 'main')
-solidus_git, solidus_frontend_git = if (branch == 'main') || (branch >= 'v3.2')
-                                      %w[solidusio/solidus solidusio/solidus_frontend]
-                                    else
-                                      %w[solidusio/solidus] * 2
-                                    end
-gem 'solidus', github: solidus_git, branch: branch
-gem 'solidus_frontend', github: solidus_frontend_git, branch: branch
+
+gem 'solidus', github: 'solidusio/solidus', branch: branch
+
+# The `solidus_frontend` gem is deprecated and isn't expected to have major
+# version updates after v3.2.
+if branch >= 'v3.2'
+  gem 'solidus_frontend'
+elsif branch == 'main'
+  gem 'solidus_frontend', github: 'solidusio/solidus_frontend', branch: branch
+else
+  gem 'solidus_frontend', github: 'solidusio/solidus', branch: branch
+end
 
 # Needed to help Bundler figure out how to resolve dependencies,
 # otherwise it takes forever to resolve them.